Aerobic and Anaerobic

Respiration

Intermediate 2 Biology

Unit 1: Living Cells

Learning Objectives

• Name the type of energy stored in food.

• Describe the energy change when food is burned.

• State the units used in measuring energy content of food.

• Define the term respiration.

• Name the food molecule that is the main source of energy in cells.

Energy Facts

• Energy facts

– Cannot be created or destroyed

– Can be converted from one form to

another

– Takes a variety of forms

– Measured in kilojoules

Energy

• Food is a store of chemical energy.

• When food is burned, chemical energy

is converted into heat and light

energy.

Energy in Living Organisms

• “Work”

– Synthesis of complex substances

– Active transport e.g. sodium-potassium pump

– Movement

– Bioluminescence

– Maintenance of body temperature

– Production of electricity

– Maintenance, repair and division

Respiration

• The chemical process by which energy

is released from cells is called

respiration.

• The main source of energy for

respiration in cells is glucose.

• This process is controlled by a series of

enzymes.

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.

Learning Objectives

• Give the full name of ATP and draw a simplified diagram of its structure.

• Name the molecule from which ATP is formed in cells and draw a simplified version of its structure.

• Explain where the energy for the formation of ATP in cells comes from.

• Explain what the energy from the breakdown of ATP is used for.

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

• If ATP is added to muscle tissue, it causes the muscle fibres to contract. The overall effect is that the muscle tissue shortens in length.

Think!!

• Explain why ATP is known as the

universal energy currency.

Learning Objectives

• Describe aerobic respiration (using the

words glucose, pyruvic acid, glycolysis,

carbon dioxide and water).

Chemistry of Respiration

• Respiration is the process by which

chemical energy is released during the

breakdown of glucose

• It occurs in every living cell

• Involves the regeneration of ATP

Regeneration of ATP

A Pi Pi

Pi

Adenosine DiPhosphate (ADP)

+ Inorganic Phosphate (Pi)

A Pi Pi Pi

Adenosine TriPhosphate (ATP)

High

energy

bond

Takes in energy

Gives out energy

Glycolysis

• Splitting of

glucose into

two molecules

of pyruvic acid

• Results in the

production of

2ATP molecules

Glycolysis

C C C

C C C

1 Glucose

C C C

C C C

2 Pyruvic Acid

2 ADP + 2Pi 2 ATP

Aerobic breakdown of pyruvic

acid

• Pyruvic acid is broken down in a series of enzyme controlled steps.

• Each pathway leads to formation of – Water

– Carbon dioxide

– 18 molecules of ATP

• As this takes place twice for each molecule of glucose the total gain of ATP is 36

Aerobic breakdown of pyruvic

acid

Investigating the activity of

enzymes in aerobic respiration

Investigating the activity of

enzymes in aerobic respiration • During respiration, glucose is broken down,

hydrogen is released at various stages

• This removal of hydrogen is controlled by an enzyme

• Yeast contains stored food which can be used as a respiratory substrate

• Resazurin dye changes colour when it gains hydrogen)

blue pink colourless

(no hydrogen) (lots of hydrogen)

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

• 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

EXPERIMENTS

Energy content of food

Release of heat energy during

respiration

Respirometer do living things produce carbon dioxide?

Respirometer

Measuring the rate of respiration

Respirometer

• A respirometer measures the rate of

respiration

• Sodium hydroxide is a chemical that

absorbs carbon dioxide

• Oxygen taken in by the animal causes

a decrease in volume in the enclosed

gas, the coloured liquid rises up the

tube.

Learning Objectives

• Describe anaerobic respiration as the breakdown of glucose to pyruvic acid by glycolysis.

• State that anaerobic respiration in animals is reversible and results in the production of lactic acid.

• Describe the effect of lactic acid on muscle cells and subsequent repayment of the oxygen debt.

• State that anaerobic respiration in plants is irreversible and results in the production of ethanol and carbon dioxide

Anaerobic Respiration

• Partial breakdown of glucose in the

absence of oxygen

• Glycolysis occurs as normal

• 2ATP are produced

• Pyruvic acid then gets converted into

– Lactic acid in animals

– Carbon dioxide and ethanol in plants and

yeast (this is irreversible)

Anaerobic Respiration in

Animals

Anaerobic Respiration in animals

• In muscles cells, lactic acid is formed during anaerobic respiration

• A build up of lactic acid reduces the efficiency of muscles leading to muscle fatigue

• Oxygen debt – is the oxygen that needs to be repaid during

a rest period

– Lactic acid is converted to pyruvic acid and respired aerobically

Anaerobic respiration in plants

and yeast

Anaerobic Respiration in plants

and yeast

• When oxygen is absent plants and

yeast respire anaerobically

– Carbon dioxide is lost from each molecule

of pyruvic acid

– Ethanol is formed

– This is irreversible

Learning Objectives

• Describe an experiment, including a

labelled diagram of the apparatus, to

investigate anaerobic respiration in

yeast and say what happens.

Comparing aerobic and

anaerobic respiration

Aerobic

respiration

Anaerobic

respiration

Need for

oxygen

Energy yield

Degree of

breakdown of

glucose

End products

Comparing aerobic and

anaerobic respiration

Aerobic

respiration

Anaerobic

respiration

Need for

oxygen

Oxygen

required

Oxygen

absent

Energy yield 38 ATP 2 ATP

Degree of

breakdown of

glucose

complete partial

End products Carbon dioxide and

water

Animals – lactic acid

Plants – ethanol and

CO2