Aerobic and Anaerobic Respiration

Intermediate 2 BiologyUnit 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

GlycolysisCCC

CCC

1 Glucose

CCC

CCC 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

Respirometerdo living things produce carbon dioxide?

RespirometerMeasuring 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 respirationAerobic respiration

Anaerobic respiration

Need for oxygenEnergy yield

Degree of breakdown of glucoseEnd products

Comparing aerobic and anaerobic respirationAerobic 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 acidPlants – ethanol and CO2