B2.1.1 Cells and cell structure B2.1.2 Dissolved

AQA Knowledge PowerPoint

Unit 2 Biology 2 B2.1 Cells and simple cell transport

PiXL AQA Knowledge PowerPoint Unit 2 Biology 2 B2 GCSE Additional Science for certification June 2014 onwards

• All living things are made up of cells. The structures of different types of cells

are related to their functions. To get into or out of cells, dissolved substances

have to cross the cell membranes.

• B2.1.1 Cells and cell structure

• B2.1.2 Dissolved substances

No Higher Tier content

B2.1.1 Cells and cell structure

Part FunctionPlant or

animal

Nucleus

Contains genetic material,

which controls the

activities of the cell

Both

Cytoplasm

Most chemical processes

take place here,

controlled by enzymes

Both

Cell

membrane

Controls the movement

of substances into and

out of the cell

Both

MitochondriaMost energy is released

by respiration hereBoth

RibosomesProtein synthesis

happens hereBoth

Cell wall Strengthens the cellPlant

ONLY

Chloroplasts

Contain chlorophyll,

absorbs light energy for

photosynthesis

Plant

ONLY

Permanent

vacuole

Filled with cell sap to help

keep the cell turgid

Plant

ONLY

All living things are made up of cells. The structures of different

types of cells are related to their functions

Yeast: Yeast is a single-celled organism.

The cells have a nucleus, cytoplasm and a

membrane surrounded by a cell wall.

Bacteria: Single-celled organism.

A bacterial cell consists of cytoplasm and

a membrane surrounded by a cell wall.

The genes are not in a distinct nucleus.

B2.1.1 Cells and cell structure - Specialised cells Cells are specialised for a particular function.

Structure helps them to carry this function out.

Cell Diagram Function Adaptations

Leaf

cell

Absorbs light for

photosynthesis.Lots of chloroplasts.

Root

hair

cell

Absorbs water and

mineral ions from the

soil.

Large finger like shapes to increase

surface area.

Sperm

cellFertilises an egg

Head contains an enzyme to help

penetrate egg, lots of mitochondria so

egg can swim to sperm.

Red

blood

cell

Carries oxygen to the

cells.

Thin outer membrane so oxygen

diffuses easily, no nucleus so more

room for oxygen.

Goblet (mucus) and cilia cells are found in the lining of

have lots of mitochondria.

Goblet (mucus) and cilia cells are found in the lining of

the gut and the tubes into the lungs. They are

specialised to release and move mucus. Helps food

slide down easily in the gut and helps trap dirt and

bacteria before they enter the lungs. The cilia cells

help move the mucus especially in the lungs. Cilia cells

have lots of mitochondria.

B2.1.2 Dissolved substances

Location Particles move From To

Small intestine

Digested food

products e.g.

glucose

Small

intestine

Blood in

capillary of

villus

Lungs

Oxygen Alveolar air

space

Blood

circulating

around the

lungs

Diffusion is the spreading of the particles of a gas or liquid,

resulting in a movement of particles from a region where

they are of a higher concentration to an area of lower

concentration.

Diffusion can occur in:

Air - smells from perfume etc.

Liquids – tea from a tea bag, dye

in water etc.

Through membranes – small intestines, blood cells etc.

Concentration gradient

A difference in

concentration between two

areas next to each other.

Particles will move down

the concentration gradient

High to Low.

The larger the difference in

concentration the faster

the rate of diffusion.


Unit 2 Biology 2 B2.2 Tissues, organs and organ systems


The cells of multicellular organisms may differentiate and become adapted for

specific functions. Tissues are aggregations of similar cells; organs are

aggregations of tissues performing specific physiological functions. Organs are

organised into organ systems, which work together to form organisms.

• B2.2.1 Animal organs

• B2.2.2 Plant organs


B2.2.1 Animal organs

Organisation of a

multicellular organism

cells →→→→ tissues →→→→ organs →→→→

organ systems

A TISSUE is a group of

specialised cells working

together to carry out a

particular function.

Tissue Function

Muscular

tissue

Contracts,

bringing about

movement

Glandular

tissue

Produces

substances such

as enzymes and

hormones

Epithelial

tissue

Covers some

parts of the

body

Tissues in the stomach The stomach is an organ

that contains:

muscular tissue, to churn

the contents

glandular tissue, to

produce digestive juices

epithelial tissue, to cover

the outside and the inside

of the stomach.

The digestive system

An organ system which humans and other mammals have so

they can exchange substances with the environment.

Part(s) Function

Pancreas/

salivary

glands

Produce

digestive juices

Stomach Digests food

Liver Produces bile

Small

intestine

Digest and

absorb soluble

food

Large

intestine

Absorbs water/

produces faeces

B2.2.2 Plant organs Tissue Definition

Epidermal Covers the plant, contains stomata.

Mesophyl Where photosynthesis takes place. Contains

palisade cells and spongy layer.

Xylem Carries water and mineral ions from roots.

Phloem Carries glucose from the mesophyll to the rest of the

plant.

Stomata Pores on the underside of the leaf that allow gases

to diffuse in and out.

Plants organs

Stem support for the leaves

and flowers. Water and

glucose transported too.

Leaves make the food for

the plant where

photosynthesis happens.

Roots anchor the plant in

the soil, take up water and

mineral ions.

Flowers are reproductive

organs to attract insects.


Unit 2 Biology 2 B2.3 Photosynthesis


Green plants and algae use light energy to make their own food. They obtain the

raw materials they need to make this food from the air and the soil. The

conditions plants are grown in can be changed to promote growth.

• B2.3.1 Photosynthesis


Photosynthesis Photo = light, Synthesis = making of (glucose)

Photosynthesis = making glucose using light

B2.3.1 Photosynthesis

Plants convert glucose into starch and store it.

Cover part of a leaf in black paper then test it for starch

using iodine.

Factors that can limit the rate of photosynthesis

• Light intensity – not enough light no photosynthesis

• CO2 concentration - not enough light no photosynthesis

• Water availability – plants wilt, not enough no

photosynthesis

• Temperature – too low temp enzymes don’t work well

Plant cells use some of the

glucose produced during

photosynthesis for respiration.

Also use the glucose to make:

oil for storage, cellulose for cell

walls, proteins (also need

nitrates for this from the soil).

Greenhouses

Farmers can use greenhouses to increase plant growth.

Artificial light - allows photosynthesis to continue beyond

daylight hours.

Heating - allows photosynthesis to continue at an

increased rate heater can also give off extra carbon

dioxide released into the greenhouse this allows

photosynthesis to continue at an increased rate.


Unit 2 Biology 2 B2.4 Organisms and their environment


Living organisms form communities, and we need to understand the relationships

within and between these communities. These relationships are affected by

external influences.

• B2.4.1 Distribution of organisms


B2.4.1 Distribution of organisms The distribution of living organisms in a particular habitat

may be affected by physical factors (abiotic) e.g.

Temperature, amount of light, availability of water,

availability of nutrients, availability of oxygen and carbon

dioxide. They can also be affected by living factors

(biotic) availability of prey, disease, predators.

Quadrats: These are square

frames, used to mark off specific

areas of ground 0.5m X 0.5m

Quadrats:

Sample an area

Random method generate numbers using

a calculator. Take several samples

Count number of organisms in each

quadrat or count the % cover.

Calculate an average from the samples

Multiply the average by the area of the

field

Improve results by taking more samples

Line Transect:Measure out an area, good for investigating changing habitats, place quadrat at regular intervals, record organisms, repeat on different line to

collect average

Valid

Data collection that is

suitable to answer the

investigation

hypothesis

Reproducible

Another group are able

to carry out the

investigation and

collect similar results


Unit 2 Biology 2 B2.5 Proteins – their functions and uses


Proteins have many functions, both inside and outside the cells of living

organisms. Proteins, as enzymes, are now used widely in the home and in

industry.

• B2.5.1 Proteins

• B2.5.2 Enzymes


B2.5.1 Proteins - Enzymes

Protein molecules are made up

of long chains of amino acids.

These long chains are folded to

produce a specific shape that

enables other molecules to fit

into the protein.

Proteins: structural components

of tissues e.g. muscles,

hormones, antibodies,

enzymes.

Enzymes made of proteins they are biological catalysts -

substances that increase the rate of chemical reactions

without being used up.

Enzymes are also easily affected by pH changes. Need specific conditions to keep them

working at their best. OPTIMUM CONDITIONS!

To begin with heat will help increase collisions

between the enzymes and substrates BUT too hot

and it will denature (remember denature NOT die)

Uses of enzymes: Biological

detergents: Contain protease and

lipase, break down protein and fats

in stains. Baby food: Protease, Pre

digest proteins. Diet products:

isomerase is used to convert glucose

syrup into fructose syrup, which is

much sweeter, can be used in

smaller quantities in slimming foods

DENATURED

B2.5.2 Enzymes –Digestive enzymes Enzymes for respiration, photosynthesis and protein

synthesis work inside cells. Other enzymes produced

by specialised cells and released from them e.g.

digestive enzymes. Catalyse means to speed up.

Enzyme Reaction

catalysed

Where produced

Amylase Starch → sugars Salivary glands,

pancreas, small

intestine

Protease Proteins → amino

acids

Stomach, pancreas,

small intestine

Lipase Lipids → faFy

acids + glycerol

Pancreas, small

intestine

: Digestion and pH:

The stomach releases acid. The enzymes made in

the stomach work best in acidic conditions. The

enzymes made in the pancreas and small intestine

work best in alkaline conditions. The liver produces

bile which is released into the small intestine. Bile

neutralises the acid that was added to the food in

the stomach.

Digestion and absorption occurs

in the gut this goes from the

mouth to the anus.


Unit 2 Biology 2 B2.6 Aerobic and anaerobic respiration


Respiration in cells can take place aerobically or anaerobically. The energy

released is used in a variety of ways. The human body needs to react to the

increased demand for energy during exercise.

• B2.6.1 Aerobic respiration

• B2.6.2 Anaerobic respirationHigher tier content: HT - As the breakdown of glucose is incomplete, much less

energy is released than during aerobic respiration. Anaerobic respiration results in

an oxygen debt that has to be repaid in order to oxidise lactic acid to carbon

dioxide and water.

B2.6.1 Aerobic respiration

Aerobic Respiration The process of releasing energy from food in cells. Aerobic respiration -

uses oxygen. All chemical reactions inside cells are controlled by enzymes.

RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY.

Glucose reacts with oxygen, producing carbon dioxide and water as waste products. To

release energy. This takes place continuously in animals and plants.

Aerobic respiration (with oxygen)

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

Released energy is used for:To build up larger molecules using smaller

ones. In animals, to enable muscles to

contract. In mammals and birds, to

maintain a steady body temperature in

colder surroundings. In plants, to build up

sugars, nitrates and other nutrients into

amino acids which are then built up into

proteins.

Mitochondria: Tiny organelles found in most

plant and animal cells. Where the respiration

reactions happen. More active cells have

more

mitochondria

e.g. muscle cells,

sperm cells.

During exercise changes take place: the heart rate and breathing increases. Blood flow

increases so more glucose and O2 to cells. Muscles store glucose as glycogen – the glycogen

gets converted back to glucose during exercise.

B2.6.2 Anaerobic respiration

During exercise, too little oxygen is reaching the muscles they use anaerobic respiration to

RELEASE energy. It is the incomplete breakdown of glucose and produces lactic acid.

RESPIRATION RELEASES ENERGY IT DOES NOT PRODUCE ENERGY.

Anaerobic respiration (without oxygen)

glucose → lacIc acid (+ small amount of energy)

Higher Tier OXYGEN dept: Anaerobic respiration results in an oxygen debt that has to be

repaid in order to change lactic acid to carbon dioxide and

water. The extra oxygen needed is called the oxygen debt.

In yeast anaerobic respiration produces ethanol and carbon dioxide (which is why

we used it to make beer and bread) we call this fermentation.

Lactic AcidIf muscles have long

periods of exercise they

get fatigued- they stop

contracting properly. One

cause is the build-up of

lactic acid in the muscles.

Lactic acid is poisonous.

We can only tolerate

small amounts in our

body. Blood flowing

through the muscles

removes the lactic acid.

-The heart continues to

pump faster.

-The breathing rate

remains high.

-This delivers the extra

oxygen to the muscles.

-This pays back the

oxygen debt.


Unit 2 Biology 2 B2.7 Cell division and inheritance


Characteristics are passed on from one generation to the next in both plants and

animals. Simple genetic diagrams can be used to show this. There are ethical

considerations in treating genetic disorders.

Higher Tier - construct genetic diagrams of monohybrid crosses and predict the

outcomes of monohybrid crosses and be able to use the terms homozygous,

heterozygous, phenotype and genotype. Foundation Tier - should be able to

interpret genetic diagrams of monohybrid inheritance and sex inheritance.

• B2.7.1 Cell divisionHigher Tier - When a cell divides to form gametes:

■ copies of the genetic information are made

■ then the cell divides twice to form four gametes, each with a single set of

chromosomes.

• B2.7.2 Genetic variationHigher Tier - Each gene codes for a particular combination of amino acids which

makes a specific protein.

• B2.7.3 Genetic disorders

Genetic information is in the nucleus of cells

Inside the nucleus are chromosomes made up of

DNA –BODY CELLS have two sets of chromosomes,

SEX CELLS (gametes) have one set of chromosomes

in humans body cells 46 chromosomes (23 pairs),

sex cells (sperm/egg) 23 single chromosomes.

BODY CELLS DIVIDE BY MITOSIS (makes my toes)

SEX CELLS DIVIDE BY MEIOSIS

B2.7.1 Cell division

MITOSIS cell division for growth and

repair of cells (produces clones).

1

2

3

4

5

6

Higher Tier MEIOSIS cell division to produce sex cells

for reproduction.

Creates 4 daughter cells, genetically

unique , makes gametes (sperm,

egg), 23 chromosomes only

1. Parent cell

2. Chromosomes

make identical

copies of

themselves

3. Line up along

the centre

4. They move

apart

5. Two daughter

cells start to form.

6. Two new

daughter cells

with identical

chromosomes to

the parent cell.

Fertilisation: where gametes

join. New cell divides by

mitosis to form baby.

B2.7.1 Cell division – STEM cells STEM CELLS: Cells that can become anything, they are

undifferentiated

Embryonic stem cells can be made into

any type of cell (curing all sorts of disease)

but come from aborted embryos (which

can be a problem) We also don't know the

long term effect of their use yet.

Adult bone marrow stem cells can also be used

but can’t be made into as many different things

but you can give permission to have them taken

the operation can be painful!

Stem cells can be used in new treatments

for Parkinson's disease and paralysis. They

can be harvested from inside embryos,

umbilical cords and bone marrow.

There are social and ethical issues

concerning the use of human embryonic

stem cells.

Plant Cells: Most plant cells stay unspecialised.

They can differentiate all through their lives.

Unspecialised cells are made at the stems and

roots, where mitosis takes place almost

constantly. This makes it very easy to clone plants.

Sexual reproduction leads to variation: Meiosis ensures that

all gametes contain the same genes, but have a different

selection of alleles. Also, it is random which sperm fertilises

which egg.

B2.7.2 Genetic variation

Alleles -different forms of the

same gene represented by two

letters. For example, eye colour

Recessive- characteristic only

expressed when two of the

same alleles are present e.g.

bb. Dominant- characteristic

expressed when one or both

alleles are present e.g. BB or Bb

HIGHER TIER:

Homozygous- two of the same allele e.g. bb or BB

Heterozygous- two different alleles e.g. Bb

Genotype- the genes present e.g. Bb or bb or BB

Phenotype- the genes that are expressed in the

physical characteristics. e.g., brown eyes, blue eye,

blond hair, brown hair. Each gene codes for a

particular combination of amino acids which makes

a specific protein.

Determining sex (gender): Human

body cells have 23 pairs of

chromosomes in the nucleus. One of

these pairs controls the inheritance

of gender: XX=female XY=male

All individuals (except for

identical twins) produced

sexually are genetically

different DNA fingerprinting

can identify individuals.

HIGHER TIER: You must be able to draw for

monohybrid crosses, these and identify

genotype and phenotype of offspring. You

must work out % of offspring with each

characteristic. T – tall t – short

What % of the offspring

will be short?

Cystic fibrosis (a disorder of

cell membranes) inherited

from both parents. The

parents can be carriers of CF

but not have CF. Caused by a

recessive allele so can passed

on by parents who don’t have

it. Causes thick, sticky mucus

to accumulate in the lungs

and the digestive system. This

causes: Lung infections,

problems with breathing,

problems with digestion and

absorption.

B2.7.3 Genetic disorders

Polydactyly: Extra fingers or toes - caused by a dominant

allele can be passed on by only one parent who has the

disorder.

Some genetic disorders are inherited e.g. polydactyly, cystic fibrosis.

Embryos can be screened for the different types of disorders.

Some genetic disorders are inherited e.g. polydactyly, cystic fibrosis.

Embryos can be screened for the different types of disorders.

A genetic

pedigree or

Family trees

can also be

used to trace

how a disease

is inherited.

On the right is

an example for

cystic fibrosis.

B2.7.2 Genetic variation – Gregor Mendel

Gregor Mendel (1822-1884) studied the

inheritance of different characteristics in

pea plants.

• Found that when he bred red-flowered

plants with white-flowered plants, all

the offspring had red flowers.

• If he bred these plants with each other,

most had red flowers, but some had

white.

• This was because the allele for red

flowers is dominant, and the allele for

white flowers is recessive.

FIRST CROSS:

All the offspring have red flowers, even though they

carry the recessive allele for white flowers

SECOND CROSS:

Three-quarters of the offspring have red flowers

and a quarter have white flowers

Called the father of modern genetics. No one

took his ideas seriously until after his death.


Unit 2 Biology 2 B2.8 Speciation


Changes in the environment of plants and animals may cause them to die out. The

fossil record shows that new organisms arise, flourish, and after a time become

extinct. The record also shows changes that lead to the formation of new species.

• B2.8.1 Old and new species

Higher Tier - genetic variation – each population has a wide range of

alleles that control their characteristics

■ natural selection – in each population, the alleles that control the

characteristics which help the organism to survive are selected

■ speciation – the populations become so different that successful

interbreeding is no longer possible.

B2.8.1 Old and new species -

OLD

FOSSILS – SHOW EVIDENCE OF EARLY LIFE FORMS.

Can be formed by

Mineralisation of the hard parts (shells, bones, teeth etc)

Some soft parts do not decay/rot, because they are buried.

Traces of the animals (footprints, burrows, faeces, etc)

Fossils can be used to gather

evidence for evolution. This

is called a fossil record.

Extinction

Permanent loss of all members

of a species.

Caused by a change:

New predators

New diseases

Loss of habitat

More successful competitor

Can’t find evidence of all earlier life forms: Many were soft-bodied, so left few traces behind

as many destroyed by geological activity.

New species arise as because of: Isolation – two populations of

a species become separated e.g geographically.B2.8.1 Old and new species -

NEW

Higher Tier:

Genetic variation – each population has a wide range of

alleles that control their characteristics.

Natural Selection

Variation –populations of organisms have variations.

Over-production –produce more young than will survive

to adulthood.

Struggle for existence – competition for survival

between the organisms

Survival – those with advantageous characteristics are

more likely to survive Advantageous characteristics

inherited – better adapted organisms are more likely to

Reproduce successfully passing on the advantageous

characteristics to their offspring in their genes.

Gradual change – over a period of time the more

individuals with the advantageous characteristics in the

population.

Higher Tier: Speciation

Takes place when an isolated

population becomes so different

from the original population that a

new species is produced.

Endemic: A species that has evolved to live in only one place in

the world.

Species: A group of similar organisms that can breed to

produce fertile offspring

Documents

B2.1.1 Cells and cell structure B2.1.2 Dissolved