B4 Module Introduction - WikispacesThe... · o Use these pages as a revision lesson before you start the first new topic. ... B4 Module Introduction continued ... B4 Exam-style questions

OCR 21st Century Science: B4 The processes of life

COLLINS NEW GCSE SCIENCE © HarperCollinsPublishers Ltd 2011

B4 Module Introduction

Pages 8−9 in the Student Book provide an introduction to this module.

When and how to use these pages

These pages summarise what students should already know from KS3 or from previous GCSE units and provide

an overview of the content that they will learn in this module.

o Use these pages as a revision lesson before you start the first new topic.

o Brainstorm everything that students remember about the different topics using the headings as a starting point. Compare your list with the points on page 8.

o Use the questions on page 8 as a starting point for class discussions.

o Ask students if they can tell you anything about the topics on the right-hand page.

o Make a note of any unfamiliar / difficult terms and return to these in the relevant lessons.

Suitable answers to the questions on page 8 are:

o The nucleus controls the functioning of the cell.

o Potato tubers contain starch in large quantities. This is relatively easy to digest and provides a good source of energy. The leaves contain very little starch.

o Your heart rate rises when you exercise because your muscles need a larger supply of food and oxygen for respiration to provide energy for exercise. The extra carbon dioxide produced also needs to be carried away more rapidly by the blood.

You could revisit these pages at the following points:

o before lesson b4_04 on speeding up photosynthesis, pages 16−17

o before lesson b4_06 on respiration, pages 22−23

o before lesson b4_09 on enzyme reactions, pages 28–29

Overview of module

Students begin by learning about the importance of plants as the only source of energy for the living world. This

leads into the requirements of photosynthesis and how plants are adapted to maximise the rate of photosynthesis.

This includes work at a cellular and molecular level and culminates with a look at limiting factors. The module then

looks at how the requirements for healthy plant growth (including light, water and minerals) affect the distribution of

plants. The module continues with a section on respiration, both aerobic and anaerobic, which leads into

microscope work on cell structure – relating cellular structures to the processes of photosynthesis and respiration.

The final part of the module looks at the chemical machinery of the cell in terms of enzyme structure and

functioning.

Obstacles to learning

Students may need extra guidance with the following terms and concepts:

Photosynthesis

Many students prefer human biology to the study of plants, so will need encouragement. In particular, students may

need encouragement to see the fundamental importance of photosynthesis in the biosphere.

Manipulating experimental data and interpreting graphs

Some students will find the collection of data that is useful, the organisation of the data and its analysis and display

demanding. The mathematical demands in the analysis of data can be difficult for some students. In particular,

students need to understand that taking an average is only valid if all the quantities being measured are the same

thing – some find this difficult and are prone to average all sorts of data that is not measuring the same variable.

Students who do not have a good understanding of graphic display might find some of the work difficult. Be

prepared to talk about how the shape of a graph shows if something is changing rapidly, increasing, staying

constant, etc. Watch out for students who draw beautiful graphs and charts, possibly with spreadsheets, but have

no real idea of what the graphs mean.

Diffusion and osmosis

Avoid use of words like ‘strong’ and ‘weak’ for solutions. Opt instead for ‘concentrated’ and ‘dilute’ to avoid

confusion with acids and alkalis which can be strong and dilute or weak and concentrated.

B4 Module Introduction continued


Minerals

Students can sometimes be confused by the names used for minerals. For example, potassium can be referred to

as potassium, potash or K in labels on fertiliser packets. They need to understand that minerals are never taken up

as elements but are combined with other chemicals, e.g. nitrogen is taken in as a nitrate ion.

Ecological surveying

Mapping of an area is often surprisingly difficult for students. It may be useful to produce a sketch map in advance of field work, with scale marks on it.

Respiration

The word ‘respiration’ is often used to mean breathing (which occurs in the lungs) but in fact it is the cellular

process of glucose breakdown to produce energy (which occur in all cells).

Students need to be clear that plants respire as well as animals. Some believe that plants do not respire or only do

so at night. Make sure that they are aware that respiration must occur at all times but that it is sometimes hidden by

photosynthesis in green plants in the light.

Observing cells

Students often find it difficult to see the structures detailed in drawings of cells in the actual cells on a microscope

slide. This can be discouraging.

Enzymes

The work on enzyme reactions requires students to deal with quite abstract concepts; some will find this difficult.

The lock-and-key mechanism for enzyme activity is a useful, visual representation and students should be

encouraged to become familiar with this.

Fermentation

Students may not find it easy to identify fermentation as a form of anaerobic respiration and link it with other

examples they have met in this topic.

Practicals in this module

In this module students will do the following practical work:

o Measuring the energy content of a range of plant materials

o Investigating uptake of water by root cells

o Looking at the effect of minerals on seed germination

o Investigating the rate of photosynthesis at different light levels

o Surveying plant distribution in a local area

o Investigating muscle fatigue in humans

o Observing and recording plant cells using optical microscopes

o Investigating enzyme activity across a range of pH values

o Investigating the effect of alcohol concentration on fermentation in yeasts

Key vocabulary covered in this module

photosynthesis �� chlorophyll �� chloroplasts

diffusion �� osmosis �� partially permeable membrane

synthesis �� amino acids �� active transport (Higher tier only)

limiting factor

identification key �� quadrat �� transect

aerobic respiration �� anaerobic respiration �� oxygen debt

cellulose �� cell membrane �� chloroplasts �� chlorophyll �� cytoplasm �� mitochondria

active site �� enzymes �� enzyme pathway �� products �� substrates

optimum �� active site �� denaturing

fermentation �� biogas



B4 Analysing, evaluating and reviewing

Pages18−19 in the Student Book prepare students for controlled assessment.


This activity provides an opportunity to build and assess the skills that students will use when analysing data and

evaluating an investigation.

Ask students to:

o read through the context and tasks, listing any terms that they do not understand

o as a whole class or in small groups, discuss the tasks to ensure that all students understand the terminology used and to clarify what is required

o work individually or in small groups to answer the questions for each task.

If time allows, ask the students to mark one another’s work using the mark scheme provided.

Notes

This activity presents students with data from an investigation and asks them to analyse, evaluate and review it.

The earlier tasks are straightforward but the later ones require more thought about the quality of the data, so

revealing students’ understanding of relevance and reliability as well as simple interpretation.

Answers Task 1

� The totals for each weed type or the average values are probably suitable.

Sample Total Average

Fish Co 134 6.7

FishWeed 115 5.75

Jones Aquatic Suppliers 3 0.15

� Accept any sensible answers, e.g. using the average reduces the table of 60 values to three which are easier to

compare.

� Factors that would need to be controlled: amount of weed, temperature of water, level of light.

Task 2

� Accept any sensible answers. The definition of outlier is not objective so if a suitable justification is provided

accept any value identified. However, the one most likely to be quoted is the value of 11 for minute 17 for the

FishWeed sample. This is significantly higher than any other FishWeed values and significantly higher than the

ones near to it at minutes 16 and 18. The low values at the start and end of the FishWeed sample and the zero

values for Jones Aquatic Suppliers would not typically be considered outliers since they seem to be part of a

consistent pattern over a few minutes.

� Accept any sensible answer based not on the data provided but on the method as described. So, students may

say that counting bubbles is not a suitable way to measure photosynthesis because the bubbles may be

variable in size. The data seems quite consistent (it does not vary erratically) but this does not mean it is

accurate.

Task 3

� The experiment certainly allows the purchaser to discount the weed from Jones Aquatic Suppliers. The figures

for the other two samples are nearer but most reasonable people would be happy to accept that FishCo’s weed

was a better buy based on this data.

� The quality of the data gathered could be improved by measuring the volume of the gas produced by collecting

it in a small test tube and sucking it out with a gas syringe. While this would improve the accuracy of the data it

may not lead to a different decision based on the investigation. A useful suggestion would be to consider

B4 Analysing, collecting and reviewing continued


running the investigation again to see if the Jones Aquatic Suppliers weed was always low quality or whether

the particular batch used in the first run was damaged in some way and unrepresentative.

Task 4

� The failure of the weed from Jones Aquatic Suppliers is concerning and would merit a repeat to check that the

weed was non-functional rather than a problem with the particular setup for that weed sample. Most of the rest

of the data appears quite consistent, even when the values are low they tend to follow a trend, e.g. low at the

start rather than being erratically spread throughout the investigation.

� Since the data is consistent it would suggest that it is repeatable with the proviso that a new sample of Jones

Aquatic Suppliers weed might be functional.

� The data provided is perfectly adequate to answer the original question posed. Jones Aquatic Supplier weed

can be discounted and most people would choose FishCo rather than FishWeed weed as it shows roughly 17%

increase in oxygen production. In this instance the increased accuracy afforded by measuring the actual

volume of the gas produced is probably not necessary given the significant difference between the two

samples.

Mark scheme

For grade E, students need to:

o Comment on how the data was collected and its accuracy or repeatability.

o Comment on the limitations to accuracy or range of data.

o Identify the factors that need to be controlled to produce results that can be used for a fair comparison.

For grades D, C, in addition they need to:

o Suggest improvements to the apparatus or techniques, or alternative ways to collect data.

o Use the general pattern of the results as a basis for assessing accuracy and repeatability.

For grades B, A, in addition they need to:

o Describe and justify improvements to the apparatus or techniques, or alternative ways to collect the data.

o Consider critically the repeatability of the evidence, accounting for any outliers.



B4 Exam-style questions

Pages 36–37 in the Student Book are exam-style questions.


These questions are based on the whole of Module B4 and cover a range of different types of questions that

students will meet in their written exams.

o The questions could be used as a revision test once you’ve completed the module.

o Work through the questions as a class as part of a revision lesson.

o Ask students to mark each other’s work, using the mark scheme provided.

o As a class, make a list of the questions that most students did not get right. Work through these as a class.

Notes on the worked example

The question provides a simple graph about the rate of photosynthesis in different light levels and asks students to

interpret this graph. Working from graphs is a task that students often find quite difficult – encourage them to

explain why the graph is the shape it is rather than simply describing its shape. The question also requires a plan of

an investigation to see if the colour of the incident light has any effect on the rate of photosynthesis. The answer

provided is a good one so is worth going through with students.

Assessment Objectives

These exam-style questions cover the Assessment Objectives as described below.

Assessment Objectives Questions

AO1 Recall, select and communicate their knowledge and understanding of science

1a, 1b, 1c, 2b, 8a, 8b, 8c

AO2 Apply skills, knowledge and understanding of science in practical and other contexts

2a, 3a, 3b, 4a, 5, 6a, 6b

AO3 Analyse and evaluate evidence, make reasoned judgements and draw conclusions based on evidence

4b, 7

Answers

These answers are also supplied on the Teacher Pack CD so that students can mark their own or their peer’s work.

Question

number

Answer Additional notes Mark

1a Sometimes 1

1b All over the body 1

1c At all times 1

2a (2.04 – 1.48) × 8 = 4.48 kg 3

2b

Increase light levels with lamps

Increase carbon dioxide levels

Add fertiliser to the plants

1 mark for each

3

3a Seawater contains large amounts of dissolved

salt

The salt drew water out of the plants by osmosis

The lack of water killed the plants

1 mark for each

3

3b Pure water would increase the concentration of

water in the bloodstream

Water would pass into the red blood cells by

osmosis

The cells would swell and could burst

1 mark for each 3

4a(i) To release flavours and break down starch 1

B4 Exam-style questions continued


4a(ii) To remove residue which could make the wine

cloudy

1

4a(iii) If yeast was added when the liquid was boiling

the yeast would be killed

1

4a(iv) Yeast required for fermentation to occur 1

4b Fermentation produces carbon dioxide

In the bottle it is trapped and is released in one

go when the bottle is opened – this makes the

wine fizzy

Wine fermenting in the open is able to lose its

carbon dioxide slowly so it remains ‘still’

1 mark each 3

5 Should include the following points:

Manure comes from food that has been digested

by animals

This food must have originally been produced by

plants by photosynthesis

Carbon released during burning is the same

carbon that had been captured by photosynthesis

by plants originally

This means the carbon released is exactly

balanced by carbon captured - so the process is

‘carbon neutral’

For 5−6 marks:

At least 3 of these points are

mentioned. The information is relevant,

clear, organised and presented in a

structured and coherent format.

Specialist terms are used appropriately.

Few, if any, errors in grammar,

punctuation and spelling

For 3−4 marks:

At least 2 of these points are

mentioned. For the most part the

information is relevant and presented in

a structured and coherent format.

Specialist terms are used for the most

part appropriately. There may be

occasional errors in grammar,

punctuation and spelling

For 1−2 marks:

One of the points is mentioned but the

answer is simplistic. There may be

limited use of specialist terms. Errors of

grammar, punctuation and spelling may

be intrusive

6

6a The sugar provides a supply of energy for the

flowers. Since they have been removed from the

plant they are not connected to sugar-producing

leaves and will run out of energy otherwise

2

6b The salt draws the water out of the cells in the

flowers by osmosis so making them wilt

2

7 Increased growth of plants means larger roots

Higher temperature allows respiration to go faster

and so provide more energy for active uptake

1 mark for each 2

8a Substrates fit into active site of enzyme molecule

Substrates change into products while attached

to the enzyme

Products do not fit the active site and so are

released

Enzyme now free to be used again

1 mark for each 4

8b Overheating shakes up protein chain changing

shape of molecule

Changed shape means the substrate cannot fit

the active site

1 mark for each 2

8c The drop in temperature reduces energy

available to molecules to react but does not

change protein molecule shape

When temperature rises the enzyme can start to

work again as no damage to the active site

1 mark for each 2



B4 Module Checklist

Pages 34–35 in the Student Book provide a student-friendly checklist for revision.


This checklist is presented in three columns showing progression, based on the grading criteria. Bold italic means

Higher tier only.

Remind students that they need to be able to use these ideas in various ways, such as:

o interpreting pictures, diagrams and graphs

o applying ideas to new situations

o explaining ethical implications

o suggesting some benefits and risks to society

o drawing conclusions from evidence they have been given.

These pages can be used for individual or class revision using any combination of the suggestions below.

o Ask students to construct a mind map linking the points on this checklist.

o Work through the checklist as a class and note the points that need further class discussion.

o Ask students to tick the boxes on the checklist worksheet (on the Teacher Pack CD) if they feel confident that they are well prepared for the topics. Students should refer back to the relevant Student Book pages to revise the points that they feel less confident about.

o Ask students to use the search terms at the foot of the relevant Student Book pages to do further research on the different points in the checklist.

o Students could work in pairs, and ask each other what points they think they can do, and why they think that they can do those, and not others.

B4 Module Checklist continued


Module summary

In the introduction to this module, students were presented with a number of new ideas. Work through the list

below as part of their revision. Ask students to write their own summaries and mind maps, using this list as a

starting point.

Photosynthesis and water transport

o photosynthesis is the ultimate source of all food for animals

o photosynthesis uses light energy to build glucose from carbon dioxide and water

o chloroplasts contain the molecule chlorophyll which absorbs light energy

o plants require a supply of minerals to grow well; these are supplied through their roots

o the distribution of plants is controlled by how well they can get light, water and mineral salts from their environment to create glucose

o water moves through living organisms by diffusion

o osmosis is a special case of water movement through a partially permeable membrane

o active transport is a way to move chemicals like minerals against a concentration gradient; it requires an energy input by the organism

Respiration

o respiration releases energy from storage chemicals for use in the organism

o aerobic respiration requires oxygen and produces carbon dioxide and water and a large amount of energy

o anaerobic respiration does not require oxygen but produces a smaller amount of energy than aerobic respiration

o anaerobic respiration in microorganisms is known as fermentation and is more varied than aerobic respiration

o fermentation is used on an industrial scale to produce a variety of useful products for humans

Cells and enzyme activity

o all cells are surrounded by a partially permeable membrane

o animal cells contain a nucleus, cytoplasm and mitochondria; plant cells often contain chloroplasts and are surrounded by a cell wall

o cells in microorganisms do not contain a nucleus

o enzymes are protein molecules that can speed up the rate of certain reactions in cells

o the lock-and-key model is a way to explain how enzymes affect reactions



Checklist B4 Aiming for A

Use this checklist to see what you can do now. Refer back to pages 10–33 if you’re not sure. Look across the rows to see how you could progress – bold italic means Higher tier only.

Remember you’ll need to be able to use these ideas in many ways:

� interpreting pictures, diagrams and graphs � applying ideas to new situations � explaining ethical implications � suggesting some benefits and risks to society � drawing conclusions from evidence you’ve been given.

Look at pages 300–306 for information about how you’ll be assessed.

Working towards an A grade

Aiming for Grade C �� Aiming for Grade A �� understand that plant and animal bodies have energy locked up in them and that some sorts of chemicals are easier to build up and break down than others

describe photosynthesis as a series of chemical reactions which produce glucose which, in turn, drives the manufacture of other complex chemicals

recall the symbol equation for photosynthesis

describe the factors that affect the rate of photosynthesis and how these may affect the distribution of plants in an area

understand how different factors can be limiting at different times in the photosynthetic reaction

understand that osmosis is a special case of diffusion; understand the importance of diffusion and osmosis to plants, in the transport of oxygen, carbon dioxide and water

understand that active transport is transport against a concentration gradient and requires energy from respiration

understand that energy from respiration is used for the synthesis of large molecules (polymers, amino acids and proteins) and for active transport (for example for the absorption of nitrates by plant roots)

understand the energy production by aerobic and anaerobic respiration systems is very different and that this has implications for the cell

recall the symbol equation for aerobic respiration

recall the reactants and products of anaerobic respiration in a) animal cells and in b) plant cells/yeast, and use the word equations

describe these cell structures and their functions, and understand how these help to organise the chemical reactions within the cell to make the cell more efficient

OCR 21st Century Science: B4 Checklist


Aiming for Grade C �� Aiming for Grade A �� understand that particular reactions need their own enzyme (the lock and key model)

explain how temperature and pH can change the efficiency of an enzyme

understand that fermentation is an example of anaerobic respiration In microorganisms and give examples of ways this reaction has been used by humans to produce useful products

understand where anaerobic respiration is most likely to occur and use word equations to describe the reaction



Checklist B4 Aiming for C

Use this checklist to see what you can do now. Refer back to pages 10–33 if you’re not sure. Look across the rows to see how you could progress – bold italic means Higher tier only.

Remember you’ll need to be able to use these ideas in many ways:

� interpreting pictures, diagrams and graphs � applying ideas to new situations � explaining ethical implications � suggesting some benefits and risks to society � drawing conclusions from evidence you’ve been given.

Look at pages 300–306 for information about how you’ll be assessed.

Working towards a C grade

Aiming for Grade E �� Aiming for Grade C �� understand that all food comes from energy captured from sunlight by photosynthesis; understand that food energy passes through the living world along food chains

understand that plant and animal bodies have energy locked up in them and that some sorts of chemicals are easier to build up and break down than others

understand that plants need water, carbon dioxide and light to make food through photosynthesis; recall the products of photosynthesis and use the word equation

recall the symbol equation for photosynthesis

describe the factors that affect the rate of photosynthesis and how these may affect the distribution of plants in an area

understand that diffusion is the movement of molecules from places of high concentration to places of lower concentration

understand that osmosis is the movement of water molecules from a dilute to a less dilute solution through a partially permeable membrane

understand that osmosis is a special case of diffusion; understand the importance of diffusion and osmosis to plants, in the transport of oxygen, carbon dioxide and water

understand that active transport is transport against a concentration gradient and requires energy from respiration

understand that energy produced by respiration in living things is used for movement and to drive other important processes in the cell

understand that energy from respiration is used for the synthesis of large molecules (polymers, amino acids and proteins) and for active transport (for example for the absorption of nitrates by plant roots)

OCR 21st Century Science: B4 Checklist


Aiming for Grade E �� Aiming for Grade C �� recall that aerobic respiration requires oxygen, and that anaerobic respiration takes place in conditions of low oxygen; recall the reactants and products of aerobic respiration and use the word equation

understand the energy production by aerobic and anaerobic respiration systems is very different and that this has implications for the cell

recall the symbol equation for aerobic respiration

recall the common structures in plant, animal and microbial cells: nucleus, cell membrane, cytoplasm, mitochondria (plant, animal and yeast cells), cell wall (plant, yeast and bacterial cells), circular DNA (bacterial cells), chloroplasts and vacuole (plant cells)

describe these cell structures and their functions, and understand how these help to organise the chemical reactions within the cell to make the cell more efficient

understand what an enzyme is and what it does to the speed of chemical reactions; understand that enzymes work best in particular, optimum conditions of temperature and pH

understand that particular reactions need their own enzyme (the lock and key model)

explain how temperature and pH can change the efficiency of an enzyme

understand that fermentation is an example of anaerobic respiration In microorganisms and give examples of ways this reaction has been used by humans to produce useful products



b4_01 Photosynthesis

Resources

Student Book pages 10−11 � Interactive Book: Matching pairs ‘Photosynthesis and respiration’ and ‘Products of photosynthesis’

Homework pack b4_01 � Files on Teacher Pack CD: b4_01_worksheet; b4_01_practical; b4_01_technician

Equipment for practical

Learning outcomes B4.1.2 understand the role of photosynthesis in making food molecules and energy available to living organisms

through food chains

B4.2.1 recall the names of the reactants and products of photosynthesis, and use the word equation:

carbon dioxide + water (+ light energy) → glucose + oxygen

B4.2. 2 recall the formulae of the reactants and products of photosynthesis, and use the symbol equation:

6CO2 + 6H2O (+ light energy) →→→→ C6H12O6 + 6O2

B4.1.3 describe photosynthesis as a series of chemical reactions that use energy from sunlight to build large food

molecules in plant cells and some microorganisms (e.g. phytoplankton)

B4.2. 3 recall the main stages of photosynthesis: a. light energy absorbed by the green chemical chlorophyll; b.

energy used to bring about the reaction between carbon dioxide and water to produce glucose (a sugar); c. oxygen

produced as a waste product

B4.2. 4 recall that glucose may be: a. converted into chemicals needed for growth of plant cells, for example

cellulose, protein and chlorophyll; b. converted into starch for storage; c. used in respiration to release energy

Ideas about Science IaS 1.2 we can never be sure that a measurement tells us the true value of the quantity being measured.

IaS 1.3 if we make several measurements of any quantity, these are likely to vary.

IaS 1.4 the mean of several repeat measurements is a good estimate of the true value of the quantity being

measured.

Numeracy focus: Carrying out calculations using experimental data, including finding the mean and the range.

In this lesson students are learning to:

� describe the process of photosynthesis

� understand the importance of photosynthesis

� understand that plants convert the glucose they produce by photosynthesis into many different chemicals

Key vocabulary

photosynthesis �� chlorophyll �� chloroplasts


Many students prefer human biology to the study of plants.The mathematical demands of the conversion of

temperature rises to joulerific values in the practical work can be difficult for some students. Students need to

understand that taking an average is only valid if all the quantities being measured are the same thing – some find

this difficult and are prone to average all sorts of data that is not measuring the same variable.

Stimuli and starter suggestions

� There are several very good television programs that show the richness of plant life in jungles or even the paddy

fields of China and South East Asia. A clip from one of these can add interest and start students thinking about

how much land is needed to feed a family of four if the supermarket is not just around the corner.

Learning activities worksheet b4_01 + practical b4_01 Low demand � Ask students for their favourite foods and list them on the board. Identify the source of each food

and trace it back to a plant – and so to the sun as the source of energy.

Organise the class into groups to carry out the energy content experiment described on the practical sheet.

Students should share their results for different foods by adding them to a central poster or table. It is always useful

to draw together results from the whole class at the end of the lesson, to reinforce key messages in the data. This

will also allow you to tackle the Idea about Science that variation in results is inevitable and that scientists often use

an average to produce a result near to the actual value. Ask students, in groups, to use the whole class results to

produce the best possible estimate of the true value of a given food’s energy content. Ask groups to describe what

b4_01 Photosynthesis continued


they did to the data and why they think their value is more accurate than others. Talk about throwing away results

that are clearly beyond the range of most.

Remind the students that food comes ultimately from photosynthesis. Use Student Book p.10. Activity 1 on the

worksheet provides a useful way to reinforce ideas about photosynthesis being a series of reactions.

Teaching and learning notes: Most students should be able to develop a sensible investigation using the

practical sheet, but be prepared to offer extra support with the collection and analysis of the numerical data.

Standard demand � Use a question and answer class discussion to draw out the idea that the products of

photosynthesis are used to build other plant structures. Many students will have the simple idea just that

photosynthesis produces sugar. In fact, most of this sugar is converted into a range of other things as shown in

Figure 3 in the Student Book. Activity 2 on the worksheet provides a complex set of data to discuss about the link

between plant growth and distribution of energy in a plant.

High demand � The section on phytoplankton (Student Book p. 11) could be extended by internet searches

looking at how these marine algae help to maintain the atmosphere of the planet and reviewing the range of values

quoted across the net for the contribution they make. For Higher tier students, emphasise that the symbol equation

for photosynthesis shows that, for every carbon dioxide taken in, a molecule of oxygen is released.

Teaching and learning notes: Remind students not to believe everything they read on internet pages.

Plenary suggestions Brainstorm on the board the reasons why scientists need to study plants. The key reasons revolve around food

production and the maintenance of the atmosphere – which will draw together the work from the lesson.

Student Book answers Q1 a) Carbon dioxide and water b) Light c) Glucose, oxygen

Q2 a) Chlorophyll b) In the chloroplasts

Q3 Carbon is built into glucose by photosynthesis and is then moved to the growing rice grain and used to build

starch. The farmer harvests the rice, gets the grain and cooks it for a well-earned supper.

Q4 a) 1015

× 0.6 = 6 × 1014

tonnes b) 0.26 × 7 000 000 000 = 1.82 × 109 Q5 6

Worksheet answers Activity 1 (Low demand)

Q1, 2, 3 Carbon dioxide enters the plant through the leaves: D; Chlorophyll in the plant absorbs energy from light:

L; Energy from light causes chlorophyll to split water into hydrogen and oxygen: D; Hydrogen reacts with

carbon dioxide to make glucose: D; Oxygen from broken water molecule diffuses out of the cells: D; Oxygen

leaves the plant through the leaves: D.

Activity 2 (Standard demand)

Q1 a) 42 g/m2 b) 36 g/m

2

Q2 a) Roots, stalk, leaves b) To make amino acids and so protein and enzymes; to build cellulose in cell walls;

respired to provide energy, etc.

Q3 a) 44/145 = 30.3% b) 36/154 = 23.4%

Activity 3 (High demand)

Q1 Increasing seed density without fertiliser tends to reduce the grain weight produced; increasing fertiliser input

increases grain weight up to a certain level and is most noticeable at medium sowing densities. The best

approach is probably to opt for a mix of the two approaches but not to push either to the highest levels.

Q2 Yes, the results would probably be different because both rainfall and sunlight levels have strong effects on the

growth of the wheat. This may lead to a different response to fertiliser and seed density planting.

Q3 Accept any sensible plan that shows appropriate use of controls, e.g. same growing conditions, (fertiliser,

irrigation, sowing density, etc.) and a suitable output measure (e.g. weight of grain produced).

Practical sheet answers Q3 The mass of the samples will vary.

Q6 Look for comments about food not being completely burned or some of the heat escaping around the sides of

the beaker and so not heating the water. Both of these will tend to reduce the value obtained.

Q7 Students may suggest a foil sheath to guide the heat towards the beaker.




P Energy in food

Objectives

In this activity you will:

� collect data about the energy content in food materials

� evaluate methods of data collection.

Be careful when using the Bunsen burner – make sure to put on your safety glasses and tie back long hair.

Be particularly careful to avoid accidents when using burning objects.

Equipment and materials

samples of dry food • –10 to 110 °C thermometer • boiling tube or small beaker •50 ml graduated cylinder

•water from the cold tap •clamp and support stand •Bunsen burner •tongs •stopwatch •balance

•heatproof mat •calculator •safety glasses

Method

1 Weigh the sample of food you plan to burn. Aim for a sample weighing between 10 g and 25 g.

2 Set up the equipment as shown in this diagram.

3 Pour 25 ml of cold water into the beaker/tube and record its temperature.

4 Put on your safety glasses and light the Bunsen burner.

5 Hold the sample of food in the tongs. Light the material by holding it in the flame of the Bunsen burner. As soon as it catches fire, move it under the beaker of water so that as much of the heat as possible goes into the water.

6 If the food stops burning, light it again quickly with the Bunsen burner.

7 When the food will no longer burn, put the hot residue down on the heatproof mat. Quickly take and record the temperature of the water in the beaker.

8 Repeat steps 3 to 7 with other food samples.



Results

Sample 1

Sample 2

Sample 3

Sample 4

mass of sample (g)

temperature of water before burning (°C)

temperature of water after burning (°C)

temperature rise (°C)

energy released by the sample (joules)

energy released per gram

Questions

1 Work out the rise in temperature for each sample and add this value to the data table.

2 Use the formula below to calculate the energy released by each food sample.

Energy released (in joules) = mass of water (g) × 4.2 × rise in temperature

3 Explain why it is not fair to compare the energy content of different samples just by using the energy released.

4 Convert the figures for energy release to energy release per gram for each sample.

5 Can you see any patterns in your answers to question 4?

6 This experiment assumes that all of the energy in the sample goes into the water and produces a temperature rise. Do you think this is a reasonable assumption? Give reasons for your answer.

7 Redesign the equipment used in this experiment to give a more accurate result. Give reasons for your modifications.

8 Look back at the data you have collected. Give each measurement a score out of 10 for accuracy: 10 means spot on; 0 means wildly out.

a) Which measurements are you least confident about?

b) How could you improve the accuracy of these measurements?

c) Are any of the measurements so inaccurate that they are causing a major problem with your result? Give a reason for your answer.



b4_01 Energy in food

Technician sheet


For each pair of students:

� samples of dry food, e.g. dry hard cheese, uncooked pasta, crisps, marshmallows

� –10 to 110°C thermometer

� 100 ml boiling tube or beaker

� 50 ml graduated cylinder

� water from the cold tap

� clamp and support stand

� Bunsen burner

� tongs

� stopwatch

� balance

� heat-proof mat

� calculator

� safety glasses

Method

See practical sheet b4_01.

Notes

� Avoid using nuts or seeds, because of the prevalence of nut allergies.

� Avoid also using leaves, as some will give off fumes.




1 The steps of the photosynthesis reaction

1 Photosynthesis is a complex reaction with many steps. Sort the steps below into a sensible sequence to form a flow chart for the photosynthesis reaction.

Oxygen leaves the plant through the leaves.

Chlorophyll in the plant absorbs energy from light.

Carbon dioxide enters the plant through the leaves.

Oxygen from broken water molecule diffuses out of the cells.

Hydrogen reacts with carbon dioxide to make glucose.

Energy from light causes chlorophyll to split water into hydrogen and oxygen.

2 Which step of the photosynthesis reaction needs light? Mark them with an L.

3 Which step of the photosynthesis reaction can continue even in the dark? Mark them with a D.

2 Improving grain yield

Some people think that adding fertiliser to wheat plants, and growing them closer together, will increase the yield of useful grain. This idea was investigated at a research station in Wales; the data is shown in the table.

Plot 1 2 3 4 5 6 7 8 9

fertiliser input (g/m2) 0 0 0 22 22 22 66 66 66

seed density (seeds/m2) 30 90 180 30 90 180 30 90 180

mass of plants (g/m2) 145 157 164 152 166 172 157 166 154

mass of grain (g/m2) 44 42 41 46 45 44 41 38 36

1 What is the yield of useful grain for each of the following:

a) no fertiliser and seed density of 90?

b) fertiliser input of 66 g m2 and seed density of 180?

2 a) Which parts of the plant are included in the total weight of the plant but not in the grain?

b) List the things the plants might use the sugar produced by photosynthesis for, other than the grain.

3 What percentage of the total plant is the grain at:

a) lowest seed density with no fertiliser?

b) highest seed density and maximum fertiliser?



3 Fertiliser and seed density

1 If you were the farmer looking to increase the yield of useful grain, would you sow seeds more densely or increase the amount of fertiliser used? Use the data in the table above to give reasons for your answer.

2 The research was done in Wales, which typically has a wet and warm summer for growing wheat. Researchers working in Kansas in the USA have a hot dry summer for wheat growing. Would you expect their results to differ from the Welsh results? Give a reason for your answer.

3 There are many different varieties of wheat that grow in different climates. Plan an investigation to look at which variety of wheat would be most suitable for growing in Kansas.



b4_02 Diffusion

Resources

Student Book pages 12−13 � Interactive Book: Drag and drop ‘Water in plant and animal cells’; Naked Scientist animation ‘How do plants live and grow?’ � Homework pack b4_02

Files on Teacher Pack CD: b4_02_practical; b4_02_technician

Equipment for practical; animation of osmosis

Learning outcomes B4.2. 8 understand that diffusion is the passive overall movement of molecules from a region of their higher

concentration to a region of their lower concentration

B4.2.10 understand that osmosis (a specific case of diffusion) is the overall movement of water from a dilute to a

more concentrated solution through a partially permeable membrane

B4.2.11 recall that the movement of water into plant roots occurs by osmosis

Ideas about Science IaS 1.2 we can never be sure that a measurement tells us the true value of the quantity being measured.

IaS 1.3 if we make several measurements of any quantity, these are likely to vary.

IaS 1.4 the mean of several repeat measurements is a good estimate of the true value of the quantity being

measured.

Numeracy focus: Manipulating data to produce percentage changes in mass.

ICT focus: Exploring online simulations and animations showing osmosis and diffusion.


� understand the importance of water to plants

� describe the processes of osmosis and diffusion

� predict the direction of water flow by osmosis

Key vocabulary

diffusion �� osmosis �� partially permeable membrane


Avoid use of words like ‘strong’ and ‘weak’ for solutions. Opt instead for ‘concentrated’ and ‘dilute’ to avoid

confusion with acids and alkalis which can be strong and dilute or weak and concentrated.


� Ask students to work in groups to estimate how much water they take in every day. Assume that soft drinks and

tea and coffee count as the same equivalent for water. The United Nations claims a person in the UK consumes

the equivalent of 150 l per day. Where does the rest of this water go?

Learning activities practical b4_02 Low demand � Use the starter discussion to lead into the notion that water is crucial for all living things, including

plants. Some of the students may well have an interest in gardening, or family members that do, and will know how

important regular watering is to the production of a good crop. The photo on Student Book p. 10 shows how the

forces that are generated by roots as they seek out water and minerals can be considerable – this further

emphasises the importance of water to plants.

Use the practical on water uptake by plant cells to show what happens to uptake rates at different concentrations.

Students should work in groups or pairs and should set up the practical early in the lesson then work through

questions 1–3 in the Student Book while the reaction is proceeding. When the practical data is complete they can

attempt the questions on the practical sheet. At this level, make sure that students can predict which way water will

flow in a given situation (from dilute to concentrated solutions) but do not worry about their understanding of the

underlying mechanism of osmosis.

Teaching and learning notes: Students will need help in setting up the experiment and in analysing the results.

Encourage students to talk about ‘concentrated’ and ‘dilute’ solutions, not ‘strong’ and ‘weak’. At lower levels of

demand, concentrate on the need for water rather than the exact mechanism for its entry into the plant.

b4_02 Diffusion continued


Standard demand � Kinetic Theory gives a good explanation of many aspects of water movement in plants. Spend

time discussing the way that random movement of particles can cause spreading out of substances. If students

grasp this idea for diffusion they quite easily understand osmosis. Students could make predictions before the

practical work about what will happen and write these down on scraps of paper. These can be pinned on a board

and reviewed at the end of the lesson when the data is available. The practical work is interesting because it

requires students to use ideas about osmosis and swelling of cells (which they cannot see) to explain weight gain

by the discs (which they can actually see). While students are waiting for the results to become available, they can

work through questions 4 and 5 in the Student Book.

Teaching and learning notes: At this stage you do not need to worry too much about the mechanisms of osmosis

although most students will manage that without any bother – the confusion often comes from quantitative

treatment of the phenomenon and talking about ‘more’ and ‘less dilute’.

High demand � Higher-attaining students will need to understand the mechanism of osmosis. Put the term

‘osmosis animation’ into a search engine and select a few video clips to show the class. Have these ready before

the beginning of the lesson. Show the clips and ask students to explain what is happening. Take time to help

students to fix the theoretical model for osmosis in their heads before asking them to predict the outcome from the

practical. The experiment is a useful illustration of the phenomenon. After setting up the practical, students can

work through questions in the book, including question 6. When experimental data is available, ask students to

compare their predictions with the actual results.

Plenary suggestions Sort students into pairs and ask one to explain to the other why plants wilt when they lose water and recover when

they are watered. They then swap over and the second member explains why people often look for fruit that is

slightly soft at the grocers but avoid buying potatoes that are soft. Why this difference? Soft potatoes have lost a lot

of water and are probably quite old and past their best whereas fruit that is slightly softer is probably ripe and ready

for eating.

Share insights from some pairs with the whole class as appropriate.

Student Book answers Q1 Any 3 from: keeping chemicals in solution, taking part in important reactions, keeping our cells the correct

shape or acting as a heat store.

Q2 20% (accept ‘up to 20%’)

Q3 70 × 57% = 39.9 kg

Q4 Glass is impermeable to water.

Q5 Because the carbon dioxide is being constantly used up by photosynthesis.

Q6 Because it allows some things (accept water) through but not others.

Practical sheet answers Q1 a) Accept any sensible answers.

c) Repeating the readings, taking averages if multiple values are available.

d) An average is likely to correct for results that vary above and below the correct value.

e) An average is only useful if you have multiple values for each data point, you could not, for example, produce

an average using data from two different tubes in this experiment.

Q2 Depends on student results. Make sure units are included for all values. Use the following formula to calculate

percentage weight change.

Percentage change in mass = ((mass at start of experiment – mass at end of experiment) / mass at start of

experiment) × 100

Q3 Depends on student results. Make sure units are included for all values.

Extension

Q5 The destroyed cell membranes are no longer semi-permeable, so the cells will not show any osmotic activity.



b4_02 Diffusion

P Water uptake by plant cells

Objectives


� decide on the concentration of cell contents in potato roots

� evaluate methods of data collection

� use results to explain how plants take up water from the soil.

This investigation looks at how water moves into a root. You will prepare a range of different solutions and then see what happens to the weight of some root segments when they are left in these solutions. If the roots take up water they will get heavier.


fresh potatoes or other root vegetables • cork borer (at least size 12) • sharp knife •

electronic balance capable of weighing to 0.001 g • paper towels • 5 boiling tubes and rack •

10 ml measuring cylinder or syringe • glass rod • 25 ml of 0.5 M sodium chloride solution

Method

Preparing the experimental solutions

Label each boiling tube with a number from 1 to 5.

1 Pour 10 ml of 0.5 M sodium chloride solution into tube 1.

2 Pour 5 ml of 0.5 M sodium chloride solution into tube 2. Add 5 ml of distilled water and stir with a dry glass rod.

3 Take 5 ml of solution from tube 2 and add to tube 3. Add 5 ml of distilled water to tube 3 and stir with a dry glass rod.

4 Take 5 ml of solution from tube 3 and place in tube 4. Add 5 ml of distilled water to tube 4 and stir with a dry glass rod.

5 Place 10 ml of distilled water in tube 5.

The table below shows the resulting experimental solutions.

Tube Sodium chloride solution (M)

1 0.5

2 0.25

3 0.125

4 0.0625

5 pure water

b4_02 Diffusion continued


Preparing the disks

1 Use the cork borer – with care – to prepare cores of fresh potato tissue.

2 Cut disks from these cores. Each disk should be about 3 mm deep.

3 Blot a collection of five disks dry with a paper towel. Weigh them with the electronic balance and note down the weight in the results table.

4 Place the five disks in boiling tube 1.

5 Repeat the procedure above until you have five disks in each of the tubes. Leave the disks for at least an hour.

Collecting the results

1 Remove the disks from tube 1, blot them dry, weigh them and note down the mass in the Results table.

2 Repeat for all the tubes.

3 Calculate values to fill in the table and then plot a suitable graph or chart to display them.

Results

Tube Mass at start Mass at end Mass change % Change in mass

1

2

3

4

5

Questions

1 a) How confident are you that all of your results are reliable?

b) Identify any data points that you think might be questionable.

c) Suggest a way to solve any problems you may have found in the answer above.

d) Why might an average be useful for some of your data?

e) Can you produce an average for results from two different tubes in the data above? Give a reason for your answer.

2 Convert the changes in mass to percentage changes in mass.

3 Plot the percentage change in mass on a line graph against the concentration of sodium chloride in the bathing solution.

4 What is the concentration of the cell contents? Hint: the point at which the graph crosses the x-axis gives you the point of zero net water movement and so a measure of the concentration of the cell contents.

Extension

5 Boiling destroys the cell membrane. How do you think your results would change if you used boiled potato disks rather than raw ones? Explain the reasons for your suggestion.



b4_02 Diffusion: water uptake by plants

Technician sheet



� fresh potatoes or other root vegetables

� cork borer (at least size 12)

� sharp knife

� electronic balance capable of weighing to 0.001g

� paper towels

� 5 boiling tubes and rack

� 10 ml measuring cylinder or syringe

� glass rod

� 25 ml of 0.5 M sodium chloride solution

Method


Notes

� Count knives out and count them in.



b4_03 Minerals in the soil

Resources

Student Book pages 14−15 � Interactive Book: Quick starter ‘Plant minerals’ � Homework pack b4_03

Files on Teacher Pack CD: b4_03_practical; b4_03_technician; b4_03_worksheet


Learning outcomes B4.3.2 understand that synthesis of large molecules includes: b. synthesis of amino acids from glucose and

nitrates, and then proteins from amino acids in plant, animal and microbial cells

B4.2.7 recall that minerals taken up by plant roots are used to make some chemicals needed by cells, including

nitrogen from nitrates to make proteins

B4.2.12 understand that active transport is the overall movement of chemicals across a cell membrane

requiring energy from respiration

B4.2.13 recall that active transport is used in the absorption of nitrates by plant roots

B4.3.1 understand that all living organisms require energy released by respiration for some chemical reactions in

cells, including chemical reactions involved in: c. active transport

Ideas about Science IaS 1.6 if a measurement lies well outside the range within which the others in a set of repeats lie, or is off a graph

line on which the others lie, this is a sign that it may be incorrect. If possible, it should be checked. If not, it should

be used unless there is a specific reason to doubt its accuracy.

IaS 2.1 it is often useful to think about processes in terms of factors which may affect an outcome (or input

variables which may affect an outcome variable).

IaS 2.2 to investigate the relationship between a factor and an outcome, it is important to control all the other

factors which we think might affect the outcome (a so-called ‘fair test’).

Numeracy focus: Carrying out calculations using fractions and percentages.


� understand the importance of minerals to plants

� understand how active transport moves substances through cells (Higher)

Key vocabulary

synthesis �� amino acids �� active transport (Higher tier only)


Students can sometimes be confused by the labels used for minerals. For example, potassium can be referred to

as potassium, potash or K on labels on fertiliser packets. Explain that minerals are never taken up as elements and

are combined with other chemicals, e.g. nitrogen is taken in as a nitrate ion.


� Show some pictures of industrial wastelands – there are a number available on the internet – and ask students to

describe the environment they see. Typical problems include loss of vegetation and lots of spoil heaps. Ask why

spoil heaps cannot support most plants and draw out the idea that the metals left in the waste are toxic.

Learning activities worksheet b4_03 + practical b4_03 Low demand � Explain that students will be investigating the effect of one heavy metal, lead, on the germination of

seeds. Students work in pairs. Ask one student in each pair to predict how lead will affect the growth of the seeds

and give a reason for their prediction. The other student asks questions to make sure they understand what is

being predicted and why. After a few moments, the pair decide if they are confident in their prediction. If so, they

note it down. If not, they amend it until they are. Their investigation will test this prediction. Stress that they will be

working with (very low levels of) toxic chemicals so they need to be very vigilant about laboratory safety.

Discuss the advantages of quantitative results (e.g. whole class sets can be created). Setting up of the practical

should take part of the lesson, leaving time to work through the Student Book material about useful minerals and

metals. The worksheet provides extra tasks.

Teaching and learning notes: Emphasise the need for careful measuring to produce solutions of the correct

concentration in the experiment. Students will need help with this. Go through safety precautions.

b4_03 Minerals in the soil continued


Standard demand � Students should be able to manage the design of the experiment with just minimal support.

Ask them to display their results using percentage germination or a similar measure. The results will typically show

the pattern of a decrease in germination and growth as the concentration of toxic metals rises. However, at certain

very low concentrations of lead nitrate, the test seeds grow better than the control (water). This apparent anomaly

is probably due to the fact that nitrates are a fertiliser and the effect of this is greater than the inhibitory effect of the

lead in this instance. When all the data from the investigation is available, have a class discussion about the results

and how well they match the predictions made earlier. Discuss when an ‘anomaly’ is significant and when it is just

an outcome of experimental error. Ask students to note down two ways to distinguish between ‘interesting

anomalies’ and ‘freak results that can be discarded’.

High demand � Discuss with Higher tier students the mechanism for the uptake of the metal ions. Ask them to

work in groups to prepare a presentation on this, with particular reference to the effect of temperature on uptake.

Each group then presents to the group next to them who will ask questions, in particular about the reasons for their

prediction about the effect of temperature on metal uptake. Students should include notions that respiration is

needed for active uptake of metals and that this is reduced at lower temperatures, so leading to a lower metal

uptake. Selected groups can present to the whole class as appropriate.

Plenary suggestions Brainstorm with students a list of the differences between uptake of water and uptake of mineral ions by plants.

Student Book answers Q1 Potassium, magnesium Q2 Rapid growth of healthy plants

Q3 Because they contain high levels of toxic metals, which would be returned to the soil if they were composted.

Q4 Accept answers that involve both collecting plants from areas with high, measured levels of lead in the soil and

testing responses in the lab. These plants could then be grown in the lab in water or soil-substitute with

measured levels of lead added by solution.

Q5 Osmosis requires no energy input but active transport of minerals requires energy from respiration. Respiration

reactions slow down in lower temperatures so energy available for active uptake is reduced.


Q1, 2 nitrates amino acids proteins for growth P, M

carbon dioxide glucose and starch energy storage P, M

phosphorus proteins growth A, P, M

magnesium chlorophyll to capture light for photosynthesis P, M

potassium enzymes to speed up reactions in the cells A, P, M


Q1 Biogrow: A, the potash levels encourage fruit growth; HealthyPlant: B, high nitrogen promotes leaf growth;

SuperGreen: C, high levels of nitrogen and potassium are particularly good for hanging baskets with limited

growing medium.


Q1 a) The uptake starts at a low level then rises smoothly up to a plateau where it levels off. b) Water uptake

hardly changes with temperature and grows at a constant rate. Nitrate uptake changes dramatically and grows

at different rates, including levelling off at high temperatures. c) The increase with temperature corresponds to

an increase in the rate of respiration with temperature. d) Water is unaffected as respiration is not involved.

Nitrate reduced significantly as energy from respiration is needed for uptake of nitrates.

Practical sheet answers Q1 The fact that lead nitrate is poisonous must be mentioned. Some students might mention the dangers of

working with scissors.

Q3 Answers might typically include: in the real world there will be other plants competing with the seeds; other toxic

metals might be present in the soil; the soil itself might have an effect on the action of the lead or the response

of the plant seeds to it.

Q4 The grass seed may respond differently to cress with lead nitrate, e.g. germinate more slowly, so the results

would not be comparable.

Q5 Run two other investigations using another nitrate salt (e.g. potassium nitrate) for one and a lead salt for the

other. The potassium nitrate seeds should show low germination rates if the nitrate is toxic and the lead salt

should have no effect. If lead is toxic the potassium nitrate solution should show normal germination while the

lead salt produces a lower level.




P Effects of heavy metals on plant growth

Objectives


� plan and carry out an investigation into the effect of lead on seed germination

� draw conclusions about the danger of lead in soil.

Spoil heaps and old mine workings often have high levels of metals such as lead in the ground. These toxic metals stop most plants from growing. In this investigation you are going to produce solutions of lead nitrate at very low concentrations and see how these affect the growth of cress seeds.

Take care – lead nitrate is POISONOUS.

Wear goggles.


lead nitrate solution (TOXIC) • measuring cylinder (10 ml) • 1 ml pipette or syringe • 5 Petri dishes •

paper towel • cress seeds

Method

The diagram shows how to prepare solutions at different concentrations. The stock solution contains roughly 20 000 parts per million (ppm) of lead. This is higher than you will find in even badly polluted mine workings. By diluting this you will end up with a range of solutions, each one 10% of the previous dilution.



Plan and carry out an investigation to find out how the concentration of lead nitrate solution affects the germination and growth of cress seedlings. By the end of your investigation you should be able to say:

• how lead nitrate affects the growth of plants

• how low the concentration of lead nitrate has to be before it has no effect

• why data collected in the field might be different from the results in the laboratory.

Results

Tube Lead concentration (ppm) Seed germination

1 20 000

2

3

4

5 0 (pure water)

Questions

1 Give two safety precautions you took while working with this equipment.

2 What is the lowest level of lead that had a measurable effect on the germination of the seeds?

3 Give two reasons why the results from your laboratory experiment might be different to ones from real mining areas.

4 One student did not have enough cress seeds for all of the dishes so he used grass seed for some instead. How may this have affected the result?

5 Another student insisted that lead in lead nitrate was a fertiliser and that it was the nitrates that were dangerous to plants. Suggest another experiment you could do to investigate this idea, explaining how you would collect and interpret your results.




Technician sheet



� supply of 0.1 M lead nitrate solution (TOXIC)

� measuring cylinder (10 ml)

� 1 ml pipette or syringe

� Petri dishes × 5

� paper towel

� cress seeds

� goggles

Method

See practical sheet b4-03.

Notes

� The growing seeds will need to be left somewhere secure while they germinate. This can take up to a week.

� Health and Safety: Lead nitrate is TOXIC.




1 Synthesis

Living things take in simple chemicals and use them to make larger, more complex molecules. This is called ‘synthesis’ and requires energy.

1 Draw a line to link the simple chemical to the complex chemical and its use in organisms.

Simple chemical Complex chemical Use in the organism

nitrates proteins to capture light for photosynthesis

carbon dioxide chlorophyll proteins for growth

phosphorus enzymes energy storage

magnesium glucose and starch to speed up reactions in the cells

potassium amino acids growth

2 Put a P by your lines that show synthesis that occurs in plants.

Put an A by your lines that show synthesis that occurs in animals.

Put an M by your lines that show synthesis that occurs in microorganisms.

2 Which fertiliser?

Potassium is useful in plants for healthy growth. Its chemical symbol is K. Many gardeners use a fertiliser with lots of potassium in it to encourage growth of flowers and fruits. Nitrogen is essential for all proteins and promotes healthy growth in plants. Gardeners use nitrogen rich fertilisers to increase the growth of healthy green leaves. Phosphorus is essential for many of the reactions going on in cells. Plants that have low levels of phosphorus often show very stunted growth and produce very little fruit.

1 Look at the labels from these fertilisers and suggest which one a gardener should use for each of the plants below. Give reasons for your choices.

a) tomato plants that have just started to produce fruit

b) a lawn in spring to encourage good growth

c) a hanging basket outside a cafe where the owner wants a good show of flowers

��

Biogrow Nitrogen: 5% Phosphates: 10% Potassium: 12%

��

HealthyPlant Nitrogen: 11% Phosphorus: 5% Potassium: 5%

----------------------------

SuperGreen Nitrogen: 24% Phosphates: 8% Potassium: 16% ----------------------------



3 Active uptake

The graph shows the uptake of two chemicals by the roots of a plant at different temperatures. Study the graph and then answer the questions below.

1 a) Describe the shape of the graph for nitrate uptake.

b) Give two differences shown between nitrate uptake and water uptake.

c) What evidence in the graph shows that nitrates are taken up actively by plants?

d) The plant was then treated with a metabolic poison that stopped respiration of glucose in the cells. Suggest how this would affect the uptake of water and of nitrates by the plant. Give reasons for your answer.



b4_04 Speeding up photosynthesis

Resources

Student Book pages 16−17 � Interactive Book: Quick starter ‘Photosynthesis limiting factors’ � Homework pack b4_04


Equipment for main practical

Learning outcomes B4.2.14 understand that the rate of photosynthesis may be limited by: a. temperature; b. carbon dioxide; c. light

intensity

B4.2.15 interpret data on factors limiting the rate of photosynthesis

Ideas about Science IaS 1.6 if a measurement lies well outside the range within which the others in a set of repeats lie, or is off a graph


be used unless there is a specific reason to doubt its accuracy


variables which may affect an outcome variable)


factors which we think might affect the outcome (a so-called ‘fair test’)


� identify the factors that affect the rate of photosynthesis

� understand the concept of a limiting factor

Numeracy focus: Plotting, drawing and interpreting graphs and charts from primary and secondary data.

Key vocabulary

limiting factor


The shape of the graph in this activity tells a story, and students who do not have a good understanding of graphic

display (this is not just about being able to draw a graph) might find some of the work difficult. Be prepared to talk

about how the shape of the graph shows if something is changing rapidly, increasing, staying constant, etc.


� Ask students to list the things needed for a long space journey – perhaps of 10 years. They are likely to come up

with food, water, oxygen and a way to clear up wastes produced (carbon dioxide and faeces). These are sensible

answers and can be extended to apply to the way the planet works – we are just a giant ‘spaceship’ flying

through space. On the planet, systems recycle materials and it is the speed at which photosynthesis works that

controls the health of our atmosphere and the amount of food available.

Learning activities practical b4_04 Low demand � Tell students that they are going to look at how much oxygen is produced by a water plant in a

given time. This data can then be used to calculate how much plant life will be needed for a trip to Mars. Ask

students to work in pairs to come up with a suitable method for measuring the rate of photosynthesis (counting the

number of bubbles is suitable at this level) . Be sure to approve the method before the practical begins. Once a

method has been agreed, ask the pairs to use it to investigate how the level of light affects the oxygen given off.

The results should show a clear increase with increased light levels but do not be surprised if the data is somewhat

messy – there are a number of factors involved here. This is a good opportunity to discuss with students how to

handle ‘rogue’ results. Encourage students to spot these (perhaps from a table of data or a point on a graph

outside the trend) and then consider whether the data can be replaced by freshly-collected data or discarded

because of an obvious error in the measuring technique or equipment.

Teaching and learning notes: Working in pairs is the best arrangement for this practical.

Standard demand � At this level, most students should be able to design their own experiment and a number may

notice other problems with the simple method, e.g. carbon dioxide levels in the water may be limiting the rate of

photosynthesis, so results will be difficult to interpret. Introduce the planning exercise with minimal guidance and

emphasise the need to think constantly about improvements in the method.

b4_04 Speeding up photosynthesis continued


Ask each pair to explain their approach to the pair next to them. The listening pair should offer a critique and

suggest possible improvements. Once the method has been finalised and the practical has been run, ask students

to share their results by adding them to a single poster or writing them on the board. When all the results are in,

review them as a class for consistency and draw out by discussion any improvements students made during the

practical, asking them to explain how they helped to generate more reliable results. Discuss the handling of rogue

results as recommended above.

Students should also complete the work on limiting factors on Student Book p. 17 (questions 3 and 4). The graphs

here can be difficult to interpret but do warrant the time spent to go through them, as this gives a powerful way to

explain the results generated by the practical investigation.

Teaching and learning notes: Encourage students to modify the method if they think they can improve it – but

beware of using results from across the class if all the groups have modified their methods.

High demand � With higher-attaining students, introduce the practical work with an emphasis on producing the

most reliable data that would allow scientists to predict with certainty the amount of plant material needed to supply

oxygen for a trip to Mars. This cannot be ‘nearly right’ – if the astronauts find they have 10% less oxygen than they

need, they would die. The practical work should be fairly straightforward for these students, who could reasonably

be expected to suggest ways to improve the method.

Students should complete the Student Book work on limiting factors, including questions 5 and 6.

When drawing together data from across the groups at the end of the lesson, ask students to suggest what factors

are limiting photosynthesis in the practical they have been doing – giving reasons for their answers.

Plenary suggestions Ask students to suggest ways to increase the rate of photosynthesis for a spaceship food and oxygen production

unit. List them on the board.

Student Book answers Q1 a) Lettuce: (1.1–0.9)/0.9 = 22.2%; Tomatoes: (6.4–4.4)/4.4 = 67.7%

b) Tomatoes

Q2 The saleable product is only part of the productivity of the crops.

Q3 A limiting factor is a factor that limits the rate of a reaction when all other relevant factors are present to excess.

Q4 a) X: Carbon dioxide

b) Y: Light

Q5 a) The rate of photosynthesis increases with temperature up to about 35 °C and then falls rapidly.

b) Accept any sensible suggestion, e.g. the higher temperature damages the enzymes needed for

photosynthesis; respiration increases at this temperature to use up the oxygen produced by photosynthesis, so

reducing the apparent rate, and the plant begins to wilt, etc.

Q6 As oxygen is used up in respiration, less will be given out and this will tend to reduce the measured rate of

photosynthesis if oxygen release is taken as the only measure.



b4_04 Speeding up photosynthesis

P Photosynthesis and light levels

Objectives


� plan and carry out an investigation into the effect of light intensity on the rate of photosynthesis

� evaluate the data collected by your investigation for reliability and accuracy.

Method

Elodea, or Canadian pondweed, provides an easy way to measure the rate of photosynthesis. Freshly cut lengths of Elodea give off oxygen in the light and it is possible to collect these bubbles and measure the volume of gas produced. Some very active plants manage to produce bubbles of oxygen rapidly enough to allow them to be counted over a measured length of time.

Plan and carry out an investigation to find out how light intensity affects the rate of photosynthesis. By the end of your investigation you should be able to say how light intensity affects the rate of photosynthesis and decide how reliable and accurate your results are.

The thoughts below may help with your investigation plan.

How can we deal with unexpected results, for example a value which seems very different from others?

How many times do we need to take a measurement to be sure it is reliable enough?

What factors will affect the rate of photosynthesis in the Elodea? How can we control these in our investigation?

Is the amount of Elodea used important?

What is the best way to collect data on the rate of photosynthesis? How can we make sure our data is reliable?



b4_04 Photosynthesis and light levels

Technician sheet



� supply of freshly-cut Elodea

� table lamps

� filter funnel (glass works best)

� test tube

� large beakers or water troughs

� syringes (5ml)

� metre rule or tape measure

Method

The standard way to do this is to place Elodea under an upended funnel in water. The gas bubbles off from the Elodea and collects in a water-filled test tube placed over the end of the funnel. Some students will measure the volume of gas given off by measuring the length of tube containing gas, others will draw off the gas with a syringe and get a more accurate measure.

The lamps provide a way to vary the level of light by moving them closer to or further away from the Elodea.

Notes

� The exact equipment requirements may change depending on the approach to the practical adopted by students. The equipment listed above is a good basic set.

� Health and Safety: care is needed as the lamps will get hot.



b4_05 Measuring plant distribution

Resources

Student Book pages 20−21 � Interactive Book: Practical investigations ‘Plant growth’ � Homework pack b4_05

Files on Teacher Pack CD: b4_05_worksheet; b4_05_practical; b4_05_technician


Learning outcomes B4.2.16 describe and explain techniques used in fieldwork to investigate the effect of light on plants, including:

a. using a light meter; b. using a quadrat; c. using an identification key

B4.2.17 understand how to take a transect

Ideas about Science IaS 1.1 data are crucial to science. The search for explanations starts from data; and data are collected to test

proposed explanations



Numeracy focus: Interpreting data collected during field work. The exact techniques used will depend on the data

gathered and the analysis but could include calculating means, assessing ranges and a variety of graphical

displays.


� describe how to measure the distribution of organisms in an area

� identify key factors affecting distribution of plants in an area

Key vocabulary

identification key �� quadrat �� transect


Mapping of an area is often surprisingly difficult for students. It may be useful to produce a sketch map in advance with scale marks on it.


Note that the work here could take more than one lesson.

� Show a photo of rhododendrons. They can produce huge impressive blooms in the spring and early summer.

The bushes can reach quite large sizes. They are being cut down in North Wales and burned (refer to Student

Book p. 20) because they are invasive and block out other species. Brainstorm ‘good’ and ‘bad’ points about

rhododendrons. Put them on a board for reference at the end of the lesson.

Learning activities worksheet b4_05 + practical b4_05 Low demand � Introduce the environmental work (practical sheet b4_05) and discuss with students the need for

reliable, objective data when considering distributions of plants and animals. It is not enough just to say there seem

to be ‘lots’ of plants here or ‘few’ animals there. Find an area local and convenient to the school, for which a risk

assessment should be done (see the technician sheet), and carry out some simple surveys of plant distribution.

Introduce the notion of using quadrats to study an area and then open up suggestions for a suitable area to study

in the school grounds. You might want students to develop their own hypotheses about plant distribution first;

worksheet b4_05 helps them with this. Paths (these often show differences in plants on trodden and untrodden

areas) or playing fields (level of coverage in the outfield and in front of the goal mouth) or differences in daisy or

plantain numbers in mown and unmown areas are suitable areas for study.

Teaching and learning notes: The practical is best done in groups with clear direction about how data are to be

collected to ensure that data from all groups can be collated into the class set. By the end all students should have

a clear understanding of the methods appropriate to study an area and an actual example of a study local to them.

Standard demand � Ask students to suggest reasons why an accurate measurement of the wildlife in a particular

area may be needed. Draw out the notion that decisions about management must be based on accurate accounts

of the environment rather than on ‘hunches’. Stress that managing a nature reserve requires us not merely to

describe what is present but also to understand the factors that are controlling distribution of wildlife so that we can

make changes to protect certain species in a predictable manner.

b4_05 Measuring plant distribution continued


In the ecological survey work, expect these students to be able to generate more of their own ideas to test and to

need less support in formulating a testable hypothesis to explain plant distribution.

By the end of the investigation students should be able to organise an ecological survey of a new area with

confidence and select appropriate mapping and measuring techniques to test an environmental hypothesis.

Teaching and learning notes: Students need to select a method of collecting data that is compatible with the way

they intend to analyse it (e.g. averages require numerical data). Encourage them to take time with the mapping –

this is important when performing subsequent analysis.

High demand � Give higher-attaining students freedom to choose an area and plot the relevant factors controlling

plant distribution in it. This could involve a few lessons work for a large project. Brainstorm possible investigations

and then ask students in groups to pick an investigation that they think is interesting and will produce useful

outcomes. Limit the range if it is too great.

Plenary suggestions Students should have identified some factors that affect the distribution of plants in an area near the school.

Showcase some of their suggestions and stress that several explanations are possible at this stage – many may be

supported by existing data. Discuss how the investigation might be taken further: what data will they collect and

how will this allow them to identify the key factor(s) controlling the plant distribution?

Student Book answers Q1 Names of plants and a measure of abundance (e.g. number of plants present in an area).

Q2 Common names may be already known by people; scientific names can be understood by people across the

globe.

Q3 a) How common a plant is in a particular area.

b) Area of field = 12 × 15 = 180 m2; Area sampled = 0.25 × 80 = 20 m

2; Percentage of field sampled =

(20/180) × 100 = 11.11%

Q4 It distributes sampling efficiently; it records the position of the plants as well as the number so allowing

ecologists to compare plant distribution with other factors, e.g. light or water levels.

Q5 Accept any sensible answer, e.g. absence of species B and C under rhododendron bush.

Q6 a) Accept any sensible answer, e.g. rhododendrons shade out other plants, they use up all water and minerals

in an area, they inhibit plants by producing toxins.

b) Accept any sensible answer that mentions particular factors and shows how these could be controlled to

check growth in the absence of rhododendrons, e.g. using cardboard to shade the ground without drawing out

water or minerals.


Q1 Accept any sensible answers. Examples include: B – Bluebells can cope with shade but cannot compete with

more aggressive plants in sunny, open areas; C – The wind on the mountaintops stops the trees growing by

cooling them down. Sheep eat the tree seedlings so none grows to maturity; D – Bananas cannot produce fruit

unless the temperature is much higher than in the UK. The sunlight in the UK is not strong enough to produce

banana fruit.


Q3 Encourage students to see that a wide variety of possible suggestions is good – provided they can be backed

up by sensible reasons.


Q1 Accept any sensible answer. The answers are likely to include the fact that numerical data are less open to

interpretation or that numerical data can be collated from a number of researchers.

Q2 Woodland path: Either grouped (under tree and in path) to compare the two areas or transects from under tree

to path to plot changes in plant populations across the boundary.

Lawn: Random, given that the area is fairly consistent – you would not expect to see major differences across

the lawn.

Beach with sand dunes: Either grouped with samples from each area or (better) as a transect to plot differences

across the area. A transect is better than grouped data here because grouping could bias the results, as you

will only take samples in areas you expect to show significant differences.




P Investigating plant distribution

Objectives


� plan an investigation using quadrats to investigate plant distribution in an area.

If you take a walk around where you live you will probably notice that plants grow in some areas but not in others. In woodland, for example, there is usually plenty of grass on the paths but brambles or ferns under the trees. On wasteland you often see clumps of stinging nettles in some places and grass in others. Why is this?

Plan an investigation to map the distribution of plants in an area near you. Your map should show numerical measurements of plants in the area.

Carry out your survey using the method described below.


quadrats 25 cm × 25 cm • tape measure (50 m)

Method

1 Clearly identify the plant which you will be investigating. Make sure everyone in your group can recognise the relevant species.

2 Place a quadrat on the ground in the study area.

3 Count the number of plants of the chosen species that are present in the area covered by the quadrat. Plants touching two sides of the quadrat are counted ‘in’, even if only a small part of the plant is touching the quadrat. Plants touching the two other sides of the quadrat are counted ‘out’.

4 Take at least 30 readings with your quadrat. Record the number of plants of the given species in each quadrat.

5 Calculate a mean value for the number of plants per quadrat.

6 Display your results in a way that seems most sensible to you.




Technician sheet



� quadrats 25 cm x 25 cm

� tape measure (50 m)

Method


Health and Safety notes

� A risk assessment of the area used and the journey to and from it should be completed.

� Care should be taken to avoid hazards such as traffic, rivers, open water, toxic plants or dog faeces.

� Some schools may have policy guidance on taking students out of the laboratory which should be consulted before planning field trips.




1 Plant distribution

Why does a plant grow well in one area but not in another? Is it because the plant needs a particular type of soil or a special range of temperature?

For each of the observations below, suggest reasons to explain the distribution of common plants. One has been done as an example for you.

Observation Possible reason

A. Poppies often grow in wheat fields but not in woodlands.

Poppies need bright sunshine and the trees in the woodland shade them, so they do not grow well.

B. Bluebells grow well in woodland but do not survive in open grasslands.

C. Mountaintops in Wales often have a good covering of grass but no trees.

D. Bananas are an important crop in many parts of the Caribbean. The plants can grow in the UK but rarely produce fruit.

2 Considering the explanations

1 Compare your answers to activity 1 above with others working near you. Do all of the explanations make sense?

2 Provide some useful feedback to people in the groups around you.

a Pick what you think is their best idea and tell them why you think it is good.

b Pick the idea you think is the weakest and suggest a way it could be improved.

c Have some people come up with very unusual suggestions?

3 Is it better to suggest one reason or many reasons to explain the plant distribution?

3 Using quadrats

1 Quadrats are a good way to measure the population of plants in an area. They can convert descriptions like ‘very rare’ and ‘common’ into numerical data, making it easier to analyse. Numerical data from different researchers can also be collated to give a larger sample size.

Give one advantage of numerical data over descriptions like ‘rare’ or ‘common’.

b4_05 Measuring plant distribution continued


2 The placing of quadrats is important. It depends on what you are investigating. Choose from the three possibilities in the table below to decide how you would place quadrats to study each of these:

• woodland path

• lawn

• beach with sand dunes.

Give reasons for your choices.

Random Grouped Transect

Advantages no chance of bias; tend to sample across the whole area

can concentrate on areas that show interesting results

makes sure samples are collected across the whole area; gathers data about what is present and where it was found

Disadvantages no data about position of quadrat

quadrats may be influenced by bias

time-consuming



b4_06 Respiration

Resources

Student Book pages 22−23 � Interactive Book: Naked Scientist animation ‘How do cells get their energy?’

Homework pack b4_06

Files on Teacher Pack CD: b4_06_worksheet

Learning outcomes B4.1.1 understand that the basic processes of life carried out by all living things depend on chemical reactions

within cells that require energy released by respiration

B4.3.1 understand that all living organisms require energy released by respiration for some chemical reactions in

cells, including chemical reactions involved in: a. movement, b. synthesis of large molecules, c. active transport

B4.3.2. understand that synthesis of large molecules includes: a. synthesis of polymers required by plant cells

such as starch and cellulose from glucose in plant cells

B4.3.3. recall that aerobic respiration takes place in animal and plant cells and some microorganisms, and

requires oxygen

B4.3.4. recall the names of the reactants and products of aerobic respiration and use the word equation:

glucose + oxygen → carbon dioxide + water (+ energy released)

B4.3.5. recall the formulae of the reactants and products of aerobic respiration and use the symbol

equation: C6H12O6 + 6O2 →→→→ 6CO2 + 6H2O



IaS 1.2 we can never be sure that a measurement tells us the true value of the quantity being measured

Numeracy/ICT focus: Calculating and manipulating data with possible use of spreadsheets.


� understand that respiration provides the energy required by living organisms

� understand how organisms use energy to build complex molecules

� recall the equation for aerobic respiration

Key vocabulary

aerobic respiration


Body shape can be very important to teenagers, so be wary of any comments made during the lesson.

The word ‘respiration’ is often used to mean breathing (which occurs in the lungs), but in fact it is the energy

reactions (which occur in all cells). Plants respire as well as animals.


� Gather photographs of bodies from the internet, ensuring a range of body sizes/shapes and ethnicities but being

careful to avoid any that are over-revealing. Present as a slideshow and ask students to identify aspects of the

body that different cultures/ages/social groupings find attractive. List these on the board.

� Inevitably the suggestion of slim body shape will arise, so use this to discuss why we can get fat. In fact, it is a

major evolutionary benefit because it means that during times of excess we store energy that will help us through

difficult times to follow. This is a useful introduction into respiration as the primary system for energy production

in the body.

Learning activities worksheet b4_06 Low demand � Stress the link between any activity in the body, such as movement, and the need for energy,

covering the word equation for respiration as given in the Student Book. Remind students that aerobic respiration

takes place in animal and plant cells and some microorganisms, and requires oxygen. Energy in food is not a bad

thing – but when we take in more energy than we need we put on weight.

Discuss with students how they might keep track of what they eat during a day. Introduce the worksheet as a way

to record the food input in a form that the whole class can use. Have a few examples of typical masses (50g, 100g,

200g) available so that students can estimate masses of the food they eat. It is surprisingly difficult to complete

b4_06 Respiration continued


such a record because there are many uncertainties but this provides a useful opportunity to talk about estimating

and uncertainty in datasets.

Standard demand � For activity 2 on the worksheet, it will help to put the class into groups to work on finding

energy contents for food. Discuss how the energy in the food is converted by respiration into energy for the body –

with the excess being converted to fat. Most students should be able to complete the calculations on the

worksheet, drawing the connection between energy intake, energy used, and fat storage in the body.

Talk about other aspects of metabolism that affect growth, e.g. the need for energy to make protein, then move on

to energy stores in plants. Plants use energy from respiration to synthesise glucose into large molecules. Polymers

such as starch act as a store of energy, and cellulose is used for cell walls. This is covered on Student Book p. 23.

An interesting extension is to ask students to identify the parts of any crop plant that we tend to eat and explain

why (it tends to be fruits and seeds which typically have a higher energy/protein content than the vegetative parts

of the plant).

Teaching and learning notes: When looking for energy values for individual foods, encourage ‘sensible guesses’

and estimates rather than letting students get bogged down in looking for exact answers. Students need to make a

clear connection between energy input and energy use by the body.

High demand � Brainstorm the things the body uses energy for. Create a spider diagram for these on the board

and ask students to suggest how the body ‘knows’ where to use the energy. Draw out the notion that certain

tissues get priority (e.g. brain). Muscles (particularly the heart) are the next priority, then down through other body

cells and ending up with fat cells using spare energy and to make fat. Emphasise that a wide range of activities

need energy; it is not just the obvious ones such as movement but also ones such as the synthesis of large

molecules and processes that use active transport.

Higher tier students need to know the symbolic equation summarising the series of respiration reactions, as given

on p. 23. It is useful to discuss why scientists use formulae when a word equation tells the same story. The major

advantage is that they give quantitative as well as qualitative data so in the respiration equation we can see that for

every oxygen molecule taken in, a single carbon dioxide molecule is given out.

Plenary suggestions Brainstorm the things that will increase and decrease body mass in humans based on the work of the lesson. Draw

out the idea that it is largely controlled by the energy balance, but that the level of activity has other effects –

regular activity tends to protect muscles against degradation, for example. Link back to the ideas presented in the

starter about body shape and the usefulness of fat to human survival.

Student Book answers Q1 Many energy-requiring processes still need to go on inside the body, e.g. keeping the brain alive, contracting

the heart muscles, etc.

Q2 The equations for photosynthesis and respiration are mirror images of each other.

Q3 a) To allow the plant to develop before it can carry out photosynthesis. b) Glucose

Q5 Cocoa has a high proportion of fat in the fruits and seeds used to make chocolate. This means chocolate has a

very high joulerific value, which tends to cause an increase in weight.

Q6 Accept any sensible answer, e.g. comparing the rate of carbon dioxide production in people using and not using

the drug at the same levels of activity (e.g. at rest). Do not accept a test that measures athletic performance –

this is more complex than simply testing the rate of respiration. There is no guarantee that an increase in

athletic performance is due to an increase in respiration rate – it might be due to other stimulants in the pill.


Q1 Depends on actual results. Watch for sensible measures for quantities (including units as appropriate).

Q2 The energy provided by the food is used in the process of respiration to provide energy for cellular processes.

Q3 Foods that have a high sugar content do have a higher energy content. However some other foods that don’t

have a high sugar content, such as starchy foods, also have high energy content.

Q4 This is so that the amount of energy per serving can be calculated, particularly for loose foods where the

amount eaten can vary a lot.


Q2 d) The excess energy may be laid down as fat deposits.

e) Either reduce the energy intake by changing the type or quantity of food, or increase the energy used by

taking more exercise.



b4_06 Respiration

1 Your energy intake

1 How much energy do you take in per day? Think carefully about a typical day from the last week and fill in the first three columns of the table on the second sheet of this worksheet. Some example entries are given below to show you how to do this.

Time Food Rough portion size Energy content

7:45 breakfast cereal (Cornflakes) 100 g

7:45 milk with cornflakes 50 ml

2 What part does this energy input play in respiration?

3 Is it true that sugary foods have a higher energy content than other foods?

4 Why do manufacturers sometimes indicate the energy content per 100 g?

2 How much energy?

1 Find out how much energy is present in each of the foods you have listed. Many labels have these figures listed on them. The internet is also a good source of information. Once you have the results, add them in the final column of the table. Remember that the values on the packet or internet might be for 100 g and you may have had more, or less, than that. Adjust the figures to match your intake.

2 a) Total your energy intake for the day. The figures below give typical energy needs for students. If you are very active, add up to 15% of the recommended value. If you are not active, cut it by up to 20%.

Basic figures Energy (kJ)

average male (15–18 years) 11 600

average female (15–18 years) 9000

b) What is the difference between the recommended value and your typical day?

c) What difference would this make over a year?

d) What happens if your energy intake is greater than your energy needs?

e) What could you do to redress this imbalance?

3 Body weight changes

1 a) 1 g of fat stores roughly 37 kJ of energy. Calculate the change to your weight over a year based on your daily energy intake and the recommended amounts.

b) Given your experience over the last year, does this result seem sensible? Look back at the data collected and the way it has been used, to find where errors might creep in. Suggest ways these might be reduced, e.g. keeping a food diary for a week rather than a day, to reduce the effect of special events such as a celebration on food intake figures.

b4_06 Respiration continued


Time Food Rough portion size Energy content



b4_07 Anaerobic respiration

Resources

Student Book pages 24−25 � Interactive Book: Quick starter ‘Anaerobic respiration’ � Homework pack b4_07



Learning outcomes B4.3.3. recall that aerobic respiration takes place in animal and plant cells and some microorganisms, and

requires oxygen

B4.3.6. recall that anaerobic respiration takes place in animal, plant and some microbial cells in conditions of low

oxygen or absence of oxygen, to include: a. plant roots in waterlogged soil, b. bacteria in puncture wounds, c.

human cells during vigorous

B4.3.7. recall the names of the reactants and products of anaerobic respiration in animal cells and some bacteria,

and use the word equation: glucose → lactic acid (+ energy released)

B4.3.9. understand that aerobic respiration releases more energy per glucose molecule than anaerobic respiration



IaS 1.5 from a set of repeated measurements of a quantity, it is possible to estimate a range within which the true

value probably lies

IaS 1.6 if a measurement lies well outside the range within which the others in a set of repeats lie, or is off a graph


be used unless there is a specific reason to doubt its accuracy

Numeracy focus: Carrying out calculations using experimental data, including finding the mean and the range.


� distinguish between aerobic and anaerobic respiration in humans

� recall word equations for anaerobic respiration

� identify energy yields for aerobic and anaerobic respiration

Key vocabulary

anaerobic respiration �� oxygen debt


This lesson will produce lots of data and some students will find this demanding in terms of: organisation, collecting

data that is useful, and display of the data (graphs and charts, etc.). Make sure students are clear about what data

they need to collect and how they will display it. Watch out for students who draw beautiful graphs and charts,

possibly with spreadsheets, but have no real idea of what the graphs mean.


� Brainstorm what students feel when they start to take exercise. The short-term symptoms will be breathlessness,

a racing heart and increased body temperature, with medium-term being muscle tiredness or aches, and long-

term being improved fitness, muscle tone and, usually, loss in body weight. Explain that in this lesson they will be

looking at the biochemical mechanisms involved with the short- and medium-term changes. Keep the list of

symptoms on a flip chart or section of the board in order to return to them at the end of the lesson.

Learning activities practical b4_07 Low demand � Introduce the experiment on the practical sheet and stress the need to avoid straining muscles –

you do not need to work particularly hard to get into anaerobic territory with some muscles. This is a good

experiment for developing skills in data manipulation and analysis, as the data produced will be fairly

straightforward and easy to display. Point out that merely ‘feeling tired’ is not a suitable output from an experiment

into muscle fatigue. Stress that numerical data gives a much clearer picture which can be analysed by statistical

methods and can be shared more easily than simple word descriptions. Take this opportunity to emphasise the IaS

outcomes given above. Agree, by discussion with the whole class, a suitable way to present data so that it can be

shared amongst the whole group at the end of the session. Discuss how the class will deal with results that seem

outside the normal range of the class values – again, this is a chance to tackle the IaS outcomes above.

b4_07 Anaerobic respiration continued


Go through the ‘Energy crisis’ section on Student Book p. 24. Make clear to students that aerobic respiration is the

‘preferred’ system as it produces more energy and less toxic waste product (lactic acid) than anaerobic respiration.

However, during strenuous exercise aerobic respiration by itself is not enough and at this point anaerobic will

become useful. Athletes exercising hard are usually using both aerobic and anaerobic respiration – do not let

students think that they switch from purely aerobic to anaerobic only.

Teaching and learning notes: The practical is a straightforward experiment but one which benefits from careful

technique and can produce useful, shareable data.

Standard demand � Students operating at this level could extend the investigation by exploring any gender

differences in the results. Other factors could also be considered, such as comparing students who are perceived

as ‘fit’ and ‘unfit’ – although the definition of these categories is problematical. It may benefit from a discussion in

the sense that athletes who engage in short explosive events like weightlifting or sprinting are likely to have a very

different response to the practical than those who train for endurance events like marathons, even though both sets

of people may be described as equally ‘fit’. A useful technique for linking theoretical knowledge to observed data is

to split the class into pairs with one half of the pair describing the results from the experiment and the other

explaining how these results fit in with (or not) with the established theory.

High demand � The practical work in this lesson is very straightforward, so higher-attaining students may benefit

from being asked to develop it themselves rather than following the instructions on the practical sheet. Do stress

the need for safety and draw out by discussion a strategy for sharing data from any different experiments that

students may design. Discuss the idea that data from exercising leg muscles may not be directly compatible with

data from exercising arm muscles but that mathematical techniques such as percentage change in heart rate or

time to muscle failure may allow patterns to be identified. Use the technique described in the Standard demand

section to encourage students to draw links between theoretical knowledge and observed data. Doing this as a

whole class can make for quite a ‘buzzy’ end to a lesson – but be careful to deal with misconceptions by going

through a few in front of the class. Students should be able to explain any patterns in their data with reference to

oxygen debt affecting the energy supply available to muscles and pain caused by the lactic acid build-up.

Plenary suggestions Looking back at the effects of exercise from the brainstorming session at the start of the lesson, ask students to

explain why we continue to breathe deeply even after exercise has finished, what causes pain in the muscle, etc.

Student Book answers Q1 Accept any sensible answers, e.g. aerobic produces carbon dioxide and water instead of lactic acid; aerobic

requires oxygen; aerobic produces more energy.

Q2 It produces toxic lactic acid and produces less useful energy than aerobic respiration.

Q3 An oxygen debt is the oxygen needed to respire away lactic acid built up during strenuous exercise by

anaerobic respiration. It is paid back by the body’s taking in more oxygen than is needed for energy supply after

the exercise is over.

Q4 It is not fair because it allows the athlete to respire aerobically more than the other runners and so gain extra

energy.

Q5 It provides too little energy and produces toxic lactic acid that cannot be removed.

Q6 X × 0.4 = 400 000; therefore X = 1 000 000.

Practical sheet answers Q1 Numerical data are more objective and can be shared across the whole class. It is also possible to use

statistical tests on numerical data (e.g. averages, totals, etc.).

Q5 Look for clear explanation in terms of muscle fatigue (without any mechanism given at lower level); higher-

attaining students should mention lactic acid build-up.

Q6 To prevent blood circulating freely and so reducing the levels of lactic acid in the muscles.

Q7 Accept any sensible suggestions that involve measurement of the interval required before first and second sets

of exercises show no differences.

Q8 a) The 23 value in Group 8, Test 1.

b) Given that the other data points from this group fit in with others in the class, it is probably safe to assume

that this result is a miscounting error and can be ignored.

c) As the investigation is looking at changes between the tests, it would be better to take averages within each

group (three averages for the whole class) rather than per group. Taking an average per group would only

reveal differences between groups, not between tests.




P Fatigue and muscle efficiency

Objectives


� explore factors affecting muscle fatigue.

Although the weights seem small, it is possible to strain finger joints if you add too many weights. Do not use weights of more than 100 g – heavier weights will not give a better result and may lead to painful injuries.


100 g mass • length of string or twine • stopwatch or clock

Method

1 Tie a piece of string around the index finger of your right hand (or your left hand if you’re left-handed) and hang a 100 g weight from it.

2 Rest your hand, palm upwards, over the edge of a bench so that your finger sticks out over the end.

3 Start the stopwatch and then raise and lower your finger as quickly as you can. Record the time it takes to complete 50 lifts of the weight in the results table below.

4 Continue lifting the weight until you cannot do any more. Record the total number of lifts you can do before your muscles fail in the results table.

5 Rest your hand for a minute, then repeat Steps 3 and 4 twice to get three sets of results.

6 Rest for a few minutes, then hold your right arm (or left arm if you’re left-handed) straight up in the air and wiggle all your fingers for 2 minutes. Your wrist should begin to ache a bit at the end of this!

7 Now repeat Steps 3 to 5 to generate three sets of data, but keep your arm pointing upwards during the rests rather than lying flat on the bench. The last set of exercises will probably be surprisingly tough for your finger!

Results

First set

Test Time to complete 50 lifts (seconds) Total number of lifts completed

1

2

3

Second set (after arm held in the air)

Test Time to complete 50 lifts (seconds) Total number of lifts completed

1

2

3

b4_07 Anaerobic respiration continued


Questions

1 Why did the experiment ask you to collect numerical data rather than just to note down how tired your muscles felt?

2 What was the total time taken to complete 50 lifts in the first data set?

3 What was the total time taken to complete 50 lifts in the second data set?

4 What differences can you see between the test results in the first set and the second set?

5 Use ideas about muscle fatigue to explain these differences.

6 Why was it important to keep your arm in the air during the second set of results while you were resting?

7 The experiment assumes that a rest of a minute in the first data set is long enough to allow the muscles to recover completely. Do your data agree with this? Explain the reasons for your answer.

8 The table below shows the data from a Year 10 group. The data shown only cover the first set of tests.

Group 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Test 1 55 64 57 61 55 56 63 23 54 60 57 58 62 56 58

Test 2 56 62 55 60 56 55 62 56 53 57 58 57 66 53 58

Test 3 57 61 59 59 55 53 60 55 58 59 55 56 61 55 58

a) Which data point seems to be an outlier?

b) What would you suggest is the best way to deal with this?

c) Two students were arguing about averages. One suggested taking an average for each test (three averages), but the other said it would be better to get an average for each person (15 averages). The experiment is designed to look at changes to muscles during exercises, so which average do you think would be more useful? Give a reason for your answer.




Technician sheet


� 100 g mass

� Length of string or twine

� Stopwatch or clock

Method



� It is possible for finger joints to be strained if students add too many weights. Do not allow them to use weights of more than 100 g – heavier weights will not give better results and may lead to painful injuries.



b4_08 Organising the cell

Resources

Student Book pages 26−27 � Interactive Book: Quick starter ‘Differences in specialised cells’; Drag and drop ‘Cells and cell structure’ � Homework pack b4_08



Learning outcomes B4.2.5 recall the structure of a typical plant cell, limited to chloroplasts, cell membrane, nucleus, cytoplasm,

mitochondria, vacuole and cell wall

B4.2.6 understand the functions of the structures in a typical plant cell that have a role in photosynthesis,

including: a. chloroplasts contain chlorophyll and the enzymes for the reactions in photosynthesis; b. cell

membrane allows gases and water to pass in and out of the cell freely while presenting a barrier to other

chemicals; c. nucleus contains DNA which carries the genetic code for making enzymes and other proteins used in

the chemical reactions of photosynthesis; d. cytoplasm where the enzymes and other proteins are made

B4.3.10 recall the structure of typical animal and microbial cells (bacteria and yeast) limited to: nucleus, cytoplasm,

cell membrane, mitochondria (for animal and yeast cells), cell wall (for yeast and bacterial cells), circular DNA

molecule (for bacterial cells)

B4.3.11 understand the functions of the structures in animal, plant, bacteria and yeast cells that have a role in

respiration, including: a. mitochondria contain enzymes for the reactions in aerobic respiration (in animals, plants

and yeast); b. cell membrane allows gases and water to pass in and out of the cell freely while presenting a barrier

to other chemicals; c. nucleus or circular DNA in bacteria contains DNA which carries the genetic code for making

enzymes used in the chemical reactions of respiration; d. cytoplasm where enzymes are made and which contains

the enzymes used in anaerobic respiration



Numeracy focus: Working out magnification ratios, as a useful extension to this lesson.

ICT focus: Loading photomicrographs of real cells from the internet (or from using digital cameras on school

microscopes) into a painting or presentation package and adding labels.


� identify the key structures in plant and animal cells

� link functions of the cell to structures in it

� explain how this system helps to organise processes in the cells

Key vocabulary

cellulose �� cell membrane �� chloroplasts �� chlorophyll �� cytoplasm �� mitochondria


Students often find it difficult to see the structures detailed in drawings of cells in the actual cells on a microscope

slide. This can be discouraging.


� Many students will already have quite a lot of knowledge about cells. This provides a good opportunity for a quiz

or brainstorm about what they already know before moving on to the main substance of the lesson. A fun way to

do this is as a game of ‘Science snap!’: mark a YES and a NO on the board and then ask two people to come out

to the front and stand on either side of the board. Ask them a question about cells that has a Yes/No answer and

then they have to slap the correct answer on the board. The first one to the correct answer wins.

Learning activities worksheet b4_08 + practical b4_08 Low demand � Microscopes are always good fun so students will want to get to this work as soon as possible.

Many of the lower-attaining students will be able to produce good drawings of cells seen through a microscope as

they are less encumbered by their knowledge about what they should see and are more likely to draw what they

actually do see. Use the section of the practical sheet ‘Drawing biological specimens’ to emphasise the technique

needed. Good drawings can be showcased at the end of the lesson either by sticking them on the wall or by taking

a quick digital photo and projecting it on the whiteboard.

b4_08 Organising the cell continued


Point out that when scientists talk about ‘data’ they usually mean numerical data but observations and drawings,

carefully done, are also a very valuable source of data in their own right.

Teaching and learning notes: Students are often nervous about drawing and produce small images – encourage

them to fill the page. Point out that this is not an exercise in producing a beautiful drawing but about recording

structures, so encourage them to add plenty of descriptive labels (in pencil).

Standard demand � A more demanding task is to abstract the structures and link them to their functions.

Encourage students to explain what they can see in terms of functioning of parts. The section about similarities and

differences on Student Book pp. 26–27 emphasises this approach. The questions help to reinforce the details

students will need to remember for their examinations. Activity 2 on the worksheet takes the material further. This is

useful when students are waiting their turn to use the microscope.

High demand � Bacterial ‘cells’ are not the same as cells for more advanced organisms. The highest-attaining

students should be able to see this and show how structures visible in simple cells can develop through evolution

into the more sophisticated structures seen in advanced cells. Emphasise notions of size as well – not all cells are

the same size. A useful technique is to ask pairs of students to prepare a simple presentation about how plant,

animal, bacterial and yeast cells carry out their particular functions. If each pair takes a single cell type they can

share their insights with other pairs around them until all the class has been exposed to all the key cell types. Ask

students to prepare material to explain how each cell type respires, grows, reproduces, takes in or manufactures

food and what kind of boundary each cell has.

Activity 3 on the worksheet is particularly demanding. You can use this as the basis for a discussion task for pairs

of students to make it more accessible.

Plenary suggestions Review the diagrams drawn by the class and pick out the features of the most successful attempts. Discuss the

difficulties the class found with locating structures in live cells (as opposed to textbook diagrams) and review the

link between structure and function for each of these.

Student Book answers Q1 Nucleus and cytoplasm

Q2 The DNA will show up clearly as a darker colour against the lighter non-stained parts.

Q3 Accept two from: chloroplasts, large cell wall, vacuole.

Q4 a) Contains the DNA (or genes) for the cell. b) Carry out respiration to convert sugar into energy that the cell

can use. c) Carry out photosynthesis to capture sunlight energy and make sugar and oxygen. (Accept just

‘making sugar’ as the production of oxygen has no benefit to the plant; it is a waste product of the process.)

Q5 Accept answers between 12 and 15 times.

Q6 As a large circular molecule of DNA loose in the cytoplasm of the cell.

Worksheet answers Activity 2 (Standard demand)

Q1 Nucleus: Contains the DNA that genetic code for making enzymes and other proteins that control the cell.

(P, A)

Chloroplast: Contains chlorophyll and other enzymes needed for photosynthesis. (P)

Cell membrane: Controls what enters and leaves the cell. (P, A, M)

Cytoplasm: Where the chemical reactions go on inside the cell. (P, A, M)

Mitochondria: Contain the enzymes needed for respiration. (P, A)

Cell wall: Stops the cell from bursting and gives the organism a firm shape. (P, M)

Large vacuole: Acts as a water store in the cell. (P)

Q2 a) 3–4 µm b) 6–7 µm c) 2 µm


Q1 a) Fat cells are not very active so do not use up a lot of energy while liver cells are very active and need a lot of

energy. The mitochondria are needed to supply the liver cells with energy.

b) The roots of a plant do not get any light and so chloroplasts would not be able to photosynthesise anyway.

The plant does not produce them below ground.

c) The nucleus contains the genetic code and passing this on is the main function of the sperm. Most other

structures have been lost to save energy. The mitochondria near the top of the tail provide energy for the

sperm tail to move.




P Observing plant cells under the microscope

Objectives


� produce slides of plant cells for viewing under a light microscope

� collect data about plant cell structure.

Cover slips are very sharp pieces of glass. Handle with care!

Wear eye protection when using iodine solution.


onion bulbs • paper towel • tweezers • microscope slides and cover slips •

iodine solution for dying starch grains black • light microscope • eye protection

Method

1 Onion bulbs are a bit like a collapsed stem. They fall apart to give thick, fleshy leaves. On the inner surface of these ‘leaves’ is a layer of cells called the epidermis. You can pull this loose with tweezers or even your fingers.

2 Put a small sample of this tissue onto a microscope slide with a drop of water and lay a cover slip on it.

3 You can add a stain such as iodine solution to make parts of the cell easier to see.

4 Produce an accurate drawing of three or four cells. Label the structures you can see. Look at the guidelines on the next sheet.



Drawing biological specimens




Technician sheet


For the class:

� a supply of fresh onions

� light microscopes


� tweezers

� paper towel

� microscope slides and cover slips

� iodine solution for staining

� eye protection

Method

See practical sheet b4-08.


� Cover slips need to be handled with extreme care to avoid breaking.

� Eye protection should be worn when using iodine solution.




1 Cell structures

Observe some plant cells under a microscope and make drawings of what you see. Be sure to add labels to identify the parts. Guidelines are given on the practical sheet.

2 Cell structures and function

1 a) Link the structure in the cell to its function with a line. One has been done as an example for you.

Structure Function

nucleus contain the enzymes needed for respiration

chloroplast stops the cell from bursting and gives the organism a firm shape

cell membrane acts as a water store in the cell

cytoplasm where the chemical reactions go on inside the cell

mitochondria contains chlorophyll and other enzymes needed for photosynthesis

cell wall contains the DNA that genetic code for making enzymes and other proteins that control the cell

large vacuole controls what enters and leaves the cell

b) Put a P next to each of the cell structures found in plants.

c) Put an A next to each of the cell structures found in animals.

d) Put an M next to each of the cell structures found in microorganisms.

2 Look at the diagrams below and on the next page and estimate the size of:

a) an animal cell nucleus b) a chloroplast c) a mitochondrion.



3 Cell specialisation

1 Use your scientific understanding of cells to explain the following observations.

a) Fat cells have very few mitochondria but very active liver cells have many.

b) Cells from the root of a plant do not contain chloroplasts.

c) The largest part of the head of a human sperm cell is the nucleus. The tail has a collar near the head that contains lots of mitochondria.



b4_09 Enzyme reactions

Resources

Student Book pages 28−29 � Interactive Book: Matching pairs ‘Enzymes’ � Homework pack b4_09

Files on Teacher Pack CD: b4_09_worksheet

Model or animation of lock and key model

Learning outcomes B4.1.4 describe respiration as a series of chemical reactions that release energy by breaking down large food

molecules in all living cells

B4.1.5 recall that enzymes are proteins that speed up chemical reactions

B4.1.6 recall that cells make enzymes according to the instructions carried in genes

B4.1.7 understand that molecules have to be the correct shape to fit into the active site of the enzyme (the

lock and key model)

Ideas about Science IaS 2.1 it is often useful to think about processes in terms of factors which may affect an outcome (or input


Literacy focus: Reading information in books and on the internet, and creating text for a particular purpose.

ICT focus: Using the internet to research a topic.


� understand the importance of enzymes

� appreciate the value of enzymes in industrial and household processes

� describe the lock and key model for enzyme action

Key vocabulary

active site �� enzymes �� enzyme pathway �� products �� substrates


This lesson requires students to work with abstract concepts and visualisations; some will find this difficult.


� Enzymes should be familiar to students from earlier work, so take this opportunity to brainstorm the information

they already have and record it on the board. Use a spider diagram or similar display technique to link together

the individual bits of knowledge the students have into a more consistent whole. Make sure you draw out, or

explain, the meanings of words like reactant, substrate and product.

Learning activities worksheet b4_09 Low demand � Following on from the starter, emphasise the idea that the key feature of enzymes is that they

speed up reactions. Make the point that this means reactions that are, effectively, too slow to measure without

enzymes, will go at a reasonable speed. Genes control the manufacture of these enzymes and so control the cell’s

reactions. The most common example of enzyme action is the digestion of food molecules and respiration. Remind

students of this fact and then introduce them to the idea that most stains on clothes are similar to foods (oil, fat,

blood, etc.) and can be digested in the same way by enzymes in laundry detergent. Introduce the worksheet and

ask students to collect information about enzymes from a variety of sources. The Student Book provides useful

information but this can be supplemented quite easily from internet searches. Divide students into groups and set

clear time limits for the task described.

Teaching and learning notes: Leave time for feedback at the end of the lesson to draw out key learning points.

Standard demand � Encourage the students to include information about the lock and key model of enzyme action

in their notes. Activity 2 on the worksheet asks students to design a laundry detergent information panel; the

guidelines are deliberately fairly flexible with regard to exact content so you could announce that the lock and key

model is specifically required.

Teaching and learning notes: Computer animations, or better still actual physical models, can help to make the

lock and key model much more accessible to students.

b4_09 Lesson continued


High demand � At this level, students should be able to complete the washing powder package panels fairly easily.

Extend the ideas involved by asking students to explain the link between genes and enzymes and stress the way

that genes control cells by controlling the enzymes that are produced. The notion of enzyme pathways can be

difficult to understand at first but it is a good way to explain how a reaction like combustion can be accomplished by

breaking it down into smaller steps – each controlled by an enzyme. A useful analogy for this is of a production line

in a factory – you can model this quite easily by constructing a pathway of students who each have to do a

particular job in making an object. Making a paper dart is a good approach – each student makes one fold and then

passes it on. You can then explore quite easily what happens if you add an extra person into the sequence to

‘double up’ one part of the process. Does it double the output of planes?

Plenary suggestions You could display the information panels produced and students could vote on which they think is the best.

Check back over the knowledge map you constructed at the start of the lesson. Ask students, ‘What do we know

now that we didn’t know then?’ and add these points to the spider diagram. It is also a good opportunity to prepare

ground for the next lesson about the rate of enzyme reactions.

Student Book answers Q1 An enzyme speeds up the rate of a reaction.

Q2 The mud is held on the fabric by fatty substances. The enzyme digests the fat so the mud does not stick to the

socks and can drift away into the washing fluid.

Q3 a) Accept any sensible answer that explains that the active site must match the shape of the substrate - not any

other chemicals.

b) Accept any sensible answer that explains that the products are not the same shape as the substrate and so

do not fit the active site.

Q4 Combustion and respiration both need oxygen and give out heat when sugar is the substrate. Combustion

gives out light and all the heat in one go so the temperature of the reacting mixture rises very rapidly.

Q5 There must be more than 20 enzymes because enzymes can only speed up a single reaction.

Worksheet answers Activity 3 (High demand)

Q1 Large complicated reactions can be broken down into smaller, simpler steps.

Q2 Accept any sensible suggestions, for example: respiration produces energy from glucose; building fat stores

energy from glucose; making of enzymes. Almost any reaction in the body will involve a series of enzymes so

accept anything that seems sensible.

Q3 a) The pathway fails at the point immediately before the missing enzyme.

b) It will have no effect on the final product as the pathway can only work as fast as the slowest link in the

chain.



b4_09 Enzyme reactions

1 Finding out about enzymes

You will be working in groups. Each group will research information about enzymes in books and on the internet.

Organise how your group will gather information about enzymes. You may want to use textbooks, the library or the internet. Agree a timescale so that different people in the group can do different things but everyone knows when they have to report back.

Use the table below to record your notes.

Have a report-back session to pool all the information your group has collected.

Question Your notes

What is an enzyme?

What does an enzyme do in the body?

What is an enzyme made of?

How can enzymes in laundry detergent help to digest stains on clothing?

What were the three most useful sites about enzymes you found?

1

2

3

b4_09 Enzyme reactions continued


2 Enzymes in washing powder

In your group, produce a suitable information panel for a manufacturer of washing powder to put on their packet/bottle. The panel should explain:

• how enzymes help to clean clothes

• the advantages of enzymes over traditional soap-based detergents.

The panel can contain up to 50 words and as many diagrams as you think works well. The panel will be 150 mm by 200 mm when it is printed on the container.

Design the panel to fill a piece of A4 paper. It will be printed at 50% of this size to give the correct size for the final panel.

1 Use the information that you researched in activity 1. Remember not all of it might be relevant or necessary.

2 Plan the panel. Organise your group so that everyone is not trying to do everything.

At the end of the lesson, all the groups’ entries will be pinned up on the wall. The class will vote for the panel that matches the specification most closely.

3 Enzyme pathways

Enzymes do not work in isolation. Many are organised into pathways.

1 Explain why pathways are more useful than single enzymes.

2 Find three examples of enzyme pathways in the human body and explain what they do.

3 What happens if one enzyme in a pathway is:

a) missing

b) works twice as fast as other enzymes in the pathway?



b4_10 Enzymes

Resources

Student Book pages 30−31 � Interactive Book: Naked Scientist animation ‘How do cells make proteins?’

Homework pack b4_10


Equipment for practical; pictures of a variety of reactions (e.g. combustion, rusting, paint drying)

Learning outcomes B4.1.8 understand that enzymes need a specific constant temperature to work at their optimum, and that they

permanently stop working (denature) if the temperature is too high

B4.1.9 explain that enzyme activity at different temperatures is a balance between: a. increased rates of

reaction as temperature increases; b. changes to the active site at higher temperatures, including

denaturing Candidates are not expected to explain why rates of reaction increase with temperature

B4.1.10 recall that an enzyme works at its optimum at a specific pH

B4.1.11 explain the effect of pH on enzyme activity in terms of changes to the shape of the active site






factors which we think might affect the outcome ( a so-called ‘fair test’)

Numeracy focus: Drawing appropriate graphs of secondary data.


� understand the factors that affect the rate of enzyme reactions

� explain how temperature affects the rate of enzyme reactions

� explain how pH affects the rate of enzyme reactions

Key vocabulary

optimum �� active site �� denaturing


The practical is fairly straightforward but some students will not notice that the sodium hydroxide solution can strip

the gelatin from the film even without the enzyme being present. If that is the case, they will assume that sodium

hydroxide solution will increase the rate of the reaction.


� Enzyme reactions are much faster than reactions with the enzyme not present. A good start to this lesson is to

discuss the notion of speed of reactions. Use pictures of a variety of reactions (e.g. combustion, rusting, paint

drying) and ask students to sort these into an order based on the speed of the reactions. Most of these will be

very straightforward and sorting will be easy. Then ask students to explain how they produced their list –

suggestions will include the rate of production of wastes or the speed at which the reactants are used up. Use

the opportunity to introduce the terms ‘reactant’ and ‘product’ to the students.

Learning activities practical b4_10 Low demand � The key issue for students to appreciate is that reactions can occur at different speeds and that the

speed of a reaction has a significant effect on the viability of a cell. Make sure students understand the term

‘optimum’ as it is applied to enzyme reactions. The practical looks at a good example of this by investigating the

effect of pH on enzyme activity. Ask students to predict what they think might happen in the various tubes. This

provides the opportunity to discuss experimental controls: explain that the tubes without the enzyme act as useful

controls. Talk to students about the rather surprising result that sodium hydroxide (clearly labelled as corrosive on

the bottle) seems to improve enzyme activity.

Teaching and learning notes: Mention that reactions are not always at their best if they are going as rapidly as

possible – the reactions that cause aging of the skin, for example, are constantly under attack from cosmetics, to

try and reduce their rate!

b4_10 Enzymes continued


Standard demand � In the practical work, as the sodium hydroxide tube (4) clears, discuss how data are crucial to

scientific work and that an unexpected result can often be useful – this is certainly not a result to dismiss. the

sodium hydroxide solution alone seems to act in the same way as the protease enzyme.

The investigation looks at qualitative data because the production of solutions with a range of pH values is difficult

in school laboratories. Draw students’ attention to the secondary data on Student Book p. 31, which gives

information about pH and enzyme digestion of protein. Students should produce the graphs needed (line graphs

are more useful than bar charts here) to display the data in the book and compare it with the all-or-nothing data

from the practical investigation. Encourage them to describe what is happening to the rate of reaction at various

points in the graph – rising, falling and level.

Teaching and learning notes: At Foundation level the mechanism to explain this range of results is unnecessary.

High demand � Higher tier students should explore the mechanism that produces the range of results and use

their ideas to explain their observations. Stress the link between molecule shape and activity – it is a good

opportunity to revise the work from the previous lesson about the lock and key mechanism of enzyme activity.

Organise students into pairs and ask them to explain to each other how denaturing an enzyme affects its activity.

Stress that once an enzyme has been denatured it cannot be re-configured to work well. The damage is

permanent. Extend the ideas here by asking them to explain how food preservation techniques often depend on

denaturing the spoilage enzymes present in most foods.

Plenary suggestions Review the results from the investigation and explain how the lock and key mechanism can explain the observed

facts. Ask students to explain how freezing or pickling can preserve food.

Student Book answers Q1 Optimum conditions are the conditions when an enzyme reaction is going as rapidly as possible.

Q2 Accept any value from 34 to 37 °C.

Q3 A line graph with the points joined by a smooth line and pH along the x-axis is most suitable here.

Q4 pH 2

Q5 Changes in pH affect the links that hold the protein chain in the correct shape. If this shape is lost the active site

will not work and so enzyme activity decreases. The answer must make reference to the lock and key model,

i.e. shape of protein and active site.

Q6 a) Vinegar has a low pH and so damages the 3D shape of the enzyme molecules. This means they cannot

digest the materials in the food to cause spoilage.

b) Freezing reduces the rate of all chemical reactions so the enzyme cannot work rapidly enough.

c) Boiling the food denatures the enzyme and by sealing it in a can no microbes from the air can get in and

spoil it.

Practical sheet answers Q1 Expect Tube 3 to clear first, although sodium hydroxide solution also degrades protein so tubes 2 and 4 may

clear.

Q2 To act as controls – to see if hydrochloric acid or sodium hydroxide solution by themselves would digest the

protein coating. A control is needed to make sure that the output variable (the film clearing) is due to the

enzyme and not the chemical added to the mixture to modify the pH.

Q3 Accept any sensible ideas but likely to include: protease works best in acid conditions; sodium hydroxide

solution can degrade film.

Q4 The extremes of pH can denature the enzyme and change the shape of the active site. This prevents it from

working properly. However, sometimes the pH can help the substrate to fit into the active site and the rate of

reaction is increased. This gives the optimum condition for the enzyme.

Q5 The reactions would all occur more slowly but the result would be the same eventually.

Q6 a) The pH of Solution 1 and the presence of the protease.

b) How much of the gelatin layer has been dissolved.

Q7 Same quantities of solution; same temperature; same amount of film; same period of time.



b4_10 Enzymes

P Investigating enzymes and pH

Objectives


� collect data about the rate of enzyme reactions in different pH solutions

� draw conclusions about the effect of pH on enzyme reactions.

Black and white photographic film consists of a celluloid surface with a gelatin layer covering its front surface. If the film has been exposed and developed, the gelatin layer contains tiny particles of silver, which make the film look black. A protein-digesting enzyme can dissolve this gelatin layer and the silver grains fall away, leaving the film clear.

Wear eye protection.


access to water bath at 30 °C • 5 test tubes • developed photographic film or 35 mm negatives •

stopwatch or digital timer • 25 ml protease solution • 5 ml pipette or syringe • 25 ml deionised water •

sodium hydroxide solution (CORROSIVE) • hydrochloric acid • scissors

Method

1 Cut the developed film into five pieces that fit easily into a test tube.

2 Label the test tubes 1 to 5.

3 Prepare tubes with the mixtures shown in the table.

Reaction mixtures:

Tube Solution 1 Solution 2

1 5 ml water 5 ml protease

2 5 ml sodium hydroxide solution 5 ml protease

3 5 ml hydrochloric acid 5 ml protease

4 5 ml sodium hydroxide solution 5 ml deionised water

5 5 ml hydrochloric acid 5 ml deionised water

4 Add a strip of exposed and developed film to each test tube and place all the tubes in

the water bath. Start the stopwatch.

5 After 1 minute, look at each piece of film and record its condition (i.e., whether it is still black or if it has cleared).

6 Repeat your observation and recording every minute for 25 minutes.

b4_10 Enzymes continued


Questions

1 Which pieces of film cleared most rapidly?

2 Why were tubes 4 and 5 needed even though they contained no protease? Use the word ‘control’ in your answer.

3 Give two conclusions you can draw from the data collected.

4 Use the lock and key mechanism to explain the results from the different tubes.

5 Predict what might happen if the investigation was repeated at 10 °C instead of in a water bath at 30 °C.

6 In this experiment what were the:

a) input variables

b) outcome variables?

7 How did you make sure that this experiment was a fair test?



b4_10 Enzymes

Technician sheet


For the class:

� water bath(s) set at 30°C (with suitable frame for supporting test tubes)


� 5 test tubes

� developed photographic film (about 2.5 to 3 cm) or two 35 mm negatives

� stopwatch or digital timer

� 25 ml protease solution (1% to 5% as suggested by the manufacturer’s instructions)

� 5 ml pipette or syringe

� 25 ml deionized water

� sodium hydroxide solution 0.01 mol dm-3

� hydrochloric acid 0.01 mol dm-3

� scissors

� eye protection

Method



� Sodium hydroxide solution is CORROSIVE. Ensure bottle is labelled as such.

� Eye protection should be worn.



b4_11 Fermentation

Resources

Student Book pages 32−33 � Interactive Book: iCould career video ‘Introduction to biofuels’ � Homework pack b4_11



Learning outcomes B4.3.8 recall the names of the reactants and products of anaerobic respiration in plant cells and some

microorganisms including yeast, and use the word equation:

glucose ヌ ethanol + carbon dioxide (+ energy released)

B4.3.12 describe examples of the applications of the anaerobic respiration of microorganisms, including the

production of biogas and fermentation in bread making and alcohol production.

Ideas about Science IaS 2.1 it is often useful to think about processes in terms of factors which may affect an outcome (or input



factors which we think might affect the outcome (a so-called ‘fair test’)


� recognise fermentation as a form of anaerobic respiration

� understand the industrial importance of fermentation

� explain how fermentation can make animal waste into valuable gas

Key vocabulary

fermentation �� biogas


Students may not find it easy to identify fermentation as a form of anaerobic respiration and reconcile it with other

examples they have met in this topic.


� Fermentation is a surprisingly common, and useful, reaction. Ask students to suggest different products that

depend on fermentation and list these on the board. To expand this introduction you might give students

5 minutes to research the topic on the internet before making the list. Typical examples will include baking,

brewing, yoghurt and cheese manufacture, vinegar production. Some students may also suggest more unusual

uses, e.g. biohol (petrol with added alcohol) or fermentation reactions in a sewage works.

Learning activities worksheet b4_11 + practical b4_11 Low demand � Introduce the idea of fermentation and stress that it is a much more varied reaction than aerobic

respiration. The exact outputs from fermentation are much more varied but all are the by-products of an organism

solving the problem of obtaining a supply of useful energy in a low-oxygen environment.

Introduce the practical investigation which looks at the effect of alcohol concentration on fermentation. Discuss the

notion of control in this investigation – is there a control? It is slightly different to the previous investigation with pH

(b4_10) as the amounts of sugar and yeast must be controlled, but we are only looking at one factor that might

have an effect (alcohol concentration) rather than pH and enzyme activity as before. Students operating at this

level may only be able to produce limited quantitative data and may opt for simple ‘tube rises/does not rise’

qualitative data. Encourage them to suggest ways this could be made more quantitative – an easy way is to

measure the height of the small tube above the mixture surface. While waiting for results from the investigation

students can do questions 1 and 2 in the Student Book and activity 1 on the worksheet.

Standard demand � Students at this level should be able to produce a variety of hypotheses to test with the yeast

experiment. Ask them to suggest why beer is often less than 10% alcohol even if there is sugar left to ferment.

Some might suggest that the yeast has died and propose that this is due to the presence of the alcohol. You may

want to revise the work about enzyme damage by extremes of pH covered in the previous lesson. Take time to

organise the class so that the results from all the different groups will be compatible. Consider how best to collect

quantitative data from each group.

b4_11 Fermentation continued


While waiting for results from the investigation, students can answer questions 3 and 4 in the Student Book and

complete activity 2 on the worksheet.

Teaching and learning notes: The investigation is relatively easy to do but measuring the rise in the tubes can be

awkward. Encourage students to consider how accurate they can be with this measurement – some will attempt to

measure to over-precise values like 0.1 mm. Explain that apparently precise measures are of limited value if they

cannot be reasonably backed up by other researchers because the equipment is not precise enough.

High demand � Students operating at the highest level should be able to plan the investigation themselves with

minimal help and obtain quantitative measures of the output. Ask them to use the lock and key model to explain the

rise and fall of yeast activity across the range of alcohol concentrations – encourage them to explain their results

rather than merely describing them. Activity 3 on the worksheet will extend this work.

Plenary suggestions Review the conditions needed for the most rapid rates of fermentation (e.g. concentration of reactants (food

supply), water levels, temperature). List these on the board and as students to explain why they encourage most

rapid fermentation reactions. Discuss with students why knowledge of these conditions might be useful to

designers of industrial units that depend on fermentation reactions.

Student Book answers Q1 Animals produce lactic acid by anaerobic respiration but microorganisms produce a wider range of products,

e.g. alcohol, methane.

Q2 As there is very little air, and so little oxygen, deep in the soil, bacteria that can respire without oxygen are at a

competitive advantage.

Q3 a) To give enough time for the yeast to produce carbon dioxide to make the bread dough rise.

b) The yeast has been killed by the cooking or the bread is too firm for rising to occur.

Q4 a) It bubbles out of the liquid.

b) If it was added before boiling, the heat would kill the fungus and so fermentation would not occur.

Q5 Methane (accept carbon dioxide although methane is more important from the angle of biogas as a fuel).

Q6 Carbon dioxide (accept water vapour)

Q7 It can be produced cheaply from a readily available source (manure).


Q1 A sugar; B alcohol (ethanol) and carbon dioxide; C lactobacillus; D making yoghurt and cheese; E acetobacter;

F ethanoic acid; G waste organic materials; H methane; I fungus; J alcohol


Q1 glucose → ethanol + carbon dioxide (+ energy released)

Q2 No, because oxygen is not required for fermentation.


Q1 a) 100 × 0.4 × 0.65 = 26 m3

b) 3500 × 106 × 45 × 0.65 = 1 × 10

11 m

3

Q2 Accept any sensible suggestions but likely to include: the ready supply of manure in more agricultural countries;

higher temperatures to speed up fermentation; relatively high cost of alternative fuels (e.g. oil and petrol) in

poorer countries.

Q3 Accept any sensible designs but features should include a method to keep the fermenting mixture warm, a way

to add more sewage and a way to collect gases.

Practical sheet answers Q1 Expect to see a reduction in yeast activity with increasing alcohol concentration.

Q4 The rising level of alcohol produced by the yeasts kills them.

Q5 a) Quality of yeast, supply of food, temperature, concentration of alcohol in the reacting mixture (this will rise as

the reaction proceeds and will eventually reduce the rate to zero).

b) Accept a sensible plan that controls yeast and sugar concentration but allows the fermentation reaction to

run to completion (this will take longer at lower temperatures). The total volume of carbon dioxide produced is a

reasonable measure of the fermentation reaction.

Q6 a) Quantity of alcohol b) Height of the solution

Q7 Same temperature; same amount of yeast solution; same time.



b4_11 Fermentation

P Fermentation and alcohol

Objectives


� collect data about the rate of fermentation in different concentrations of alcohol

� draw conclusions about the effect of alcohol on yeast cells and the implications of this for the brewing industry.

Wear eye protection.

Do not have naked flames lit when working with alcohol as it gives off vapour which may ignite.


5 boiling tubes • 5 small test tubes • access to water bath at 35 °C • yeast solution • 10 ml syringe •

sucrose solution • alcohol solution (50% ethanol in water)

Method

1 Put the five boiling tubes in a rack and insert a small test tube in each, upside down. Label each boiling tube with a number from 1 to 5.

2 Mix 10 ml of yeast solution with 15 ml of sucrose solution.

3 Add 5 ml of this mixture to tubes 1 to 5.

4 Then add:

1 ml of alcohol solution to tube 1




nothing to tube 5.

5 Put the tubes in the water bath and leave for 30 minutes, or leave overnight if no water bath is available.

6 To collect results, measure the height of the small test tube showing above the level of the yeast and sugar solution.

b4_11 Fermentation continued


Questions

1 Draw up a table showing the concentration of alcohol in the starting mixture and the height of the small test tube at the end of the experiment.

2 Describe any pattern you can see in this data and explain why it has formed.

3 What is the highest alcohol concentration that could be produced by a fermenting yeast and sugar mixture?

4 There is no living yeast in a bottle of wine even though the original fermenting mixture was well supplied with yeasts. How can you explain the lack of yeast in the wine?

5 a) List the factors that will affect the rate of fermentation used by a company brewing alcoholic drinks.

b) One company claims that the amount of alcohol produced by yeast at lower temperatures is higher than at warmer temperatures. Plan a fair test to see if this is true.

6 In this experiment what were the:

a) input variables

b) outcome variables?

7 How did you make sure that this experiment was a fair test?



b4_11 Fermentation

Technician sheet


For the class:

� water bath at 35°C


� 5 boiling tubes

� 5 small test tubes

� yeast solution

� 10 ml syringe

� sucrose solution

� 50% ethanol in water solution

� eye protection

Method



� Ensure that there is no naked flame in the laboratory, as this could ignite the alcohol.

� Eye protection should be worn.



b4_11 Fermentation

1 Using fermentation

Complete A to J in the table below, using information from page 32 of the Student Book.

Microorganism Acts on Produces Use of product

yeast sugar alcohol and carbon

dioxide making alcoholic drinks

yeast A B making bread

C milk lactic acid D

E wine F making vinegar

microorganisms in manure

G H a useful fuel gas

I rice J making the strong Chinese drink bai ju

2 The fermentation reaction

1 Write out the word equation for fermentation of sugar by yeast.

2 Would providing a constant supply of oxygen to yeast mixtures increase the rate of alcohol production? Give a reason for your answer.

3 Gas production from organic waste

Material Gas m3 per kg Percentage methane

sewage sludge 0.4 65

poultry manure 0.45 65

commercial food waste 0.55 75

domestic food waste 0.55 75

1 Use the table above to answer these questions.

a) How much methane would 100 kg of sewage sludge produce if it was fermented in a biogas digester?

b) Internet sources state that 3500 million kg of poultry manure are produced each year in the UK. How much methane could be produced if all of this was fermented?

2 Biogas digesters are used much more often in Africa and India than in the UK. Suggest two reasons for this.

3 Design a suitable manure digester for the UK. Add labels to your show how each part of your design helps to increase the rate of fermentation.

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B4 Module Introduction - WikispacesThe... · o Use these pages as a revision lesson before you start the first new topic. ... B4 Module Introduction continued ... B4 Exam-style questions