Anaerobic respiration

Question 1

Why does anaerobic respiration happen?

Answer 1

In the absence of oxygen there is no final electron acceptor so the electron transport chain stops.
Conversion of pyruvate to lactate by NADH regenerates NAD so glycolysis can continue and a small amount of ATP can be produced.

Question 2

In which organisms does anaerobic respiration lead to the production of ethanol?

Answer 2

Certain bacteria, fungi (e.g. yeast) and certain cells of higher plants (e.g. root cells when waterlogged)

Question 3

What happens to pyruvate in anaerobic respiration when it leads to the production of ethanol?

Answer 3

Carbon dioxide is removed from it (decarboxylation), this produces ethanal. Ethanal then accepts Hydrogen from reduced NAD therefore ethanal is reduced to ethanol and NADH is oxidised to NAD.

Question 4

How is the production of ethanol by yeast exploited by humans?

Answer 4

To brew beer (fermentation)

Question 5

In which organisms does anaerobic respiration lead to the production of lactate?

Answer 5

Animals

Question 6

What happens to pyruvate in anaerobic respiration when it leads to the production of lactate?

Answer 6

It accepts hydrogen from NADH to form lactate. Pyruvate is reduced, NADH is oxidised.

Question 7

7. What does lactate cause when it accumulates in muscles?

Answer 7

Muscle fatigue

Question 8

What happens to the lactate as it is produced in muscles?

Answer 8

It is removed by the blood and taken to the liver to be converted into glycogen

Question 9

What happens to lactate when oxygen is again present?

Answer 9

It is oxidised to produce pyruvate again (this is an oxygen debt)

Question 10

Is ATP production during anaerobic respiration oxidative or substrate level phosphorylation?

Answer 10

Substrate level (because it is just glycolysis that occurs!)