Respiration: anaerobic (C1)

Question 1

Anaerobic respiration definition, ATP yield, products

Answer 1

• takes place in the absence of oxygen
• small yield of ATP (2) only substrate level phosphorylation
• animals: lactate produced
• yeast cells: co2 and ethanol

Question 2

Stages involved in anaerobic respiration

Answer 2

only GLYCOLYSIS can occur

Question 3

What cannot occur in anaerobic resp. and why?

What happens to NAD?

Answer 3

without oxygen the reduced NAD (and reduced FAD) cannot be reoxidised and therefore made available to pick up more hydrogen - oxygen is the final electron acceptor
• the link reaction and the Krebs cycle cannot take place;
• glycolysis can take place as the reduced NAD formed in glycolysis transfers the hydrogen to pyruvate to form lactic acid in animals and ethanol and carbon dioxide in plants; NAD becomes reoxidised and regenerated

Question 4

Energy budget of the breakdown of glucose

under conditions

Answer 4

Anaerobic (mammalian muscle given):
• net 2 ATPs in glycolysis (substrate-level phosphorylation)
• 2 reduced NAD formed in glycolysis are oxidised when 2 pyruvates are reduced to a lactate
i.e pyruvate is not transferred to the mitochondrion and finally oxidized to carbon dioxide, but is reduced to ethanol or lactic acid in the cytoplasm.