Aerobic and anaerobic respiration

Question 1

Aerobic respiration

Answer 1

Mammals and birds need energy to maintain a constant body temperature. Energy is also needed for the following life processes: growth, cell division, muscle contraction,protein synthesis, active transport, nerve impulses

Question 2

Respiration

Answer 2

involves chemical reactions that break down nutrient molecules in living cells to release energy.

Question 3

Aerobic respiration

Answer 3

needs oxygen. It is the release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen.

Question 4

Formula

Answer 4

C6H12O6 + 6O2 → 6CO2 + 6H2O

glucose + oxygen → carbon dioxide + water

Question 5

Aerobic respiration

Answer 5

Aerobic respiration happens all the time in animals and plants. Note that respiration is different to breathing (ventilation). Most of the reactions in aerobic respiration happen inside mitochondria in cells.

Question 6

Anaerobic respiration

Answer 6

Unlike aerobic respiration, anaerobic respiration does not need oxygen. It is the release of a relatively small amount of energy in cells by the breakdown of food substances in the absence of oxygen.

Question 7

Anaerobic respiration in muscles

Answer 7

Anaerobic respiration happens in muscles during hard exercise:
glucose → lactic acid
C6H12O6 → 2C3H6O3

Question 8

Glucose

Answer 8

Glucose is not completely broken down, so much less energy is released than during aerobic respiration.

Question 9

Lactic acid

Answer 9

There is a build-up of lactic acid in the muscles during vigorous exercise. The lactic acid needs to be oxidised to carbon dioxide and water later.

Question 10

Oxygen debt

Answer 10

This causes an oxygen debt - known as excess post-exercise oxygen consumption (EPOC) - that needs to be ‘repaid’ after the exercise stops. This is why we keep on breathing deeply for a few minutes after we have finished exercising.