Background knowledge

• This is the required background knowledge:

• State three uses of energy in living things

• Give an example of an energy conversion in a living organism

• State that fats and oils contain more energy per gram than carbohydrates

• State that oxygen is required for aerobic respiration

• State the word equation for aerobic respiration

• State that CO2 is a product of aerobic respiration

• State that heat may be produced by respiration

• Describe anaerobic respiration and compare it with aerobic respiration

• Explain the working of a simple respirometer.

Learning outcomes

energy release

• To understand the importance of ATP as a means of transferring chemical energy

• To state the structure of ATP

• To describe the production of ATP

• To describe the role of ATP in cell processes

• To explain the terms oxidation and reduction

Effect of ATP on muscle fibres

• This experiment shows that the energy

for muscle contraction comes from

ATP

Structure of ATP

• Adenosine triphosphate (ATP)

– Adenosine

– Three phosphate groups

• Diagram of ATP

ATP

• a high energy molecule

• continually being hydrolysed and

resynthesised.

Formation and breakdown of

ATP

• The combining of ADP + Pi to make ATP is an energy requiring process.

• The breakdown of ATP to ADP + Pi is an energy releasing process.

• The energy required for the formation of ATP from ADP + Pi comes from the respiration of glucose.

Transfer of chemical energy by ATP

Role of ATP

• ATP is the energy source for:

– Muscle contraction

– Cell division

– Building up (synthesis) of proteins

– Transmission of nerve impulses

– Active transport

Think!!

• Explain why ATP is known as the

universal energy currency.

Metabolism

• Metabolism – All reactions that take place within the

organism

– Anabolism • Build up of larger, more complex molecules

from smaller, simpler ones

– Catabolism • Breakdown of complex molecules into smaller,

simpler ones

• Releases energy

Redox Reactions

• Oxidation – Loss of electrons

– Loss of hydrogen atoms

• Reduction – Gain of electrons

– Gain hydrogen atoms

• If one substrate becomes oxidised another becomes reduced.

OIL RIG

Oxidation and Reduction

Substrate reduced Substrate oxidised

Oxidation

Hydrogen removed

Energy released

Reduction

Hydrogen added

Energy gained

Testing your progress

• Energy is defined as the ability to do ________________.

• The energy of motion is known as ___________ energy, whereas _________ energy is stored energy.

• Living organisms need energy for many reasons – __________ reactions in which simple

molecules are built up into complex ones

– The movement of material by __________ against a concentration gradient.

Progress questions

• Fireflies can produce light in a process

called bioluminescence. Outline the

energy transformations that occur in

fireflies as they use energy from their

food to produce luminescence.

• Comment on the statement below.

– Respiration produces energy to form ATP.

ERQ – 10 marks

• Discuss the role of ATP in living matter

Chemistry of Respiration

Chapter 4

Higher Biology

Unit 1: Cells

Respiration

• The complete oxidation of glucose

during aerobic respiration takes place

in three stages:

– Glycolysis

– Krebs Cycle

– Cytochrome system

Hydrogen acceptor and carrier

• Hydrogen release from respiratory

substrate is temporarily bound to a

coenzyme which acts as a hydrogen

acceptor

– NAD = coenzyme

– NADH2= reduced coenzyme

Glycolysis

• Oxidation of Glucose (6 carbon) to

two molecules of 3-carbon pyruvic

acid.

• Occurs in cytoplasm

• Net gain of 2 ATP molecules.

• Hydrogen is released and combines

with NAD to form NADH2

• oxygen is not required.

Glycolysis

Glucose (6C)

2 x Pyruvic acid (3C)

Investigating dehydrogenase

enzymes in yeast

• As glucose is oxidised, hydrogen is

released

• The release of hydrogen is called

dehydrogenation, this controlled by

dehydrogenase enzymes.

• Resazurin dye changes from blue to

colourless as it is reduced.

Investigating the activity of enzymes in

aerobic respiration

• Set up the three test tubes as shown

below. – 10ml glucose

– 10ml yeast

– 5 ml dye

Investigating the activity of

enzymes in aerobic respiration

• Shake tubes vigorously for 20 seconds, and place in a water bath set at 37oC.

• Leave for a few minutes and observe what happens

• Draw a diagram of your results

• Can you explain your results.

Investigating the activity of

dehydrogenase enzyme in yeast

• Tube A

– Colour change from blue via pink to

colourless.

– Hydrogen has been rapidly released and

has reduced the dye.

– For this to happen – enzymes present in

yeast cells must have acted on the

glucose, the respiratory substrate, and

oxidised it.

Investigating the activity of

dehydrogenase enzyme in yeast

• Tube B – Change from blue – pink – colourless

– Reaction is slower since no glucose was added.

– enzymes could only act on any small amount of respiratory substrate already present in the yeast cells.

• Tube C – Boiling has killed the yeast and denatured the

enzymes.

Aerobic Respiration

• Kreb’s cycle

– Occurs in the matrix of mitochondria

• Cytochrome system

– Across the inner mitochondrial membrane

Structure of Mitochondria

• Mitochondria have a double plasma

membrane surrounding a fluid filled

matrix

• The inner mitochondrial membrane is

folded into cristae which provide a

large surface area for the attachment

of stalked particles.

Fate of pyruvic acid

• Molecules of pyruvic acid enter the cells

mitochondria.

• Mitochondria are sausage shaped

organelles surrounded by a double

plasma membrane.

• The inner membrane is folded into

cristae,

– provide a large surface area for the stalked

particles on which ATP is produced.

Fate of pyruvic acid

• Pyruvic acid diffuses into the matrix of the mitochondria

• pyruvic acid is converted into 2C acetyl coenzyme A (Acetyl CoA),

• Hydrogen is released and combines with NAD

• Carbon dioxide is released – Enzymes that control the release of CO2

are called decarboxylases.

Kreb’s Cycle

• Acetyl CoA (2C) combines with a 4 carbon compound to form citric acid (6C).

• Citric acid is coverted back into the 4 carbon compound by decarboxylation (removal of CO2) and dehydrogenation.

• Enzymes involved in these steps are dehydrogenases and decarboxylases.

• Hydrogen combines with NAD to form NADH2.

Cytochrome System

• NADH2 (reduced coenzyme) transfers hydrogen to a chain of hydrogen carriers known as Cytochrome system.

• Each carrier molecule is alternately reduced and oxidised.

• The hydrogen from each NADH2 releases energy to form 3 ATP molecules from ADP and Pi.

• This process is known as oxidative phosphorylation.

• Oxygen is the final hydrogen acceptor to form water (controlled by cytochrome oxidase)

Respiratory Substrates

• Fats and proteins can also be used as

respiratory substrates

Respiratory substrates

Glycogen or starch

Glucose

Pyruvate

Acetylcoenzyme A

Krebs cycle

Protein

Amino Acids

Lipid

fatty Acids

Anaerobic Respiration

• Partial breakdown of glucose

• If oxygen absent only glycolysis can

occur

• Glucose is broken down to two

molecules of pyruvic acid, with a net

yield of 2 ATP molecules.

Anaerobic respiration in plants

(and yeast)

Glucose (6C)

pyruvic acid (3C)

ethanol (2C) + CO2

Anaerobic respiration in animals

• Glucose pyruvic acid lactic acid

• During lactic acid formation an

oxygen debt is build up

Respirometer

Respirometer

• Sodium hydroxide absorbs all CO2 from the air in the apparatus from the beginning.

• As the germinating seeds use oxygen and the pressure reduces in tube A so the manometer level nearest to the seeds rises.

• Any CO2 excreted is absorbed by the sodium hydroxide solution.

Respirometer

• The syringe is used to return the manometer

fluid levels to normal.

• The volume of oxygen used is calculated by

measuring the volume of gas needed from

the syringe to return the levels to the original

values

• If water replaces the sodium hydroxide then

amount of carbon dioxide given off can be

measured

Simple Respirometers

Na-K pump

• 3 Na+ leave the cell

• 2 K+ enter the cell

• Potential difference is created across

the neurone membrane for nerve

impulses.

Key

1

3

• Summary of

the sodium

potassium

pump!