Anaerobic Respiration

Question 1

Alcoholic fermentation (yeast)

Answer 1

Pyruvate decarboxylated by pyruvate decarboxylase to form ethanal. Ethanal reduced by ethanol dehydrogenase to ethanol. Reduced NAD supplies the H needed, so its oxidised to NAD which can be used in glycolysis to produce a small amount of ATP by substrate level phosphorylation.

Question 2

Lactate Fermentation (mammals)

Answer 2

Pyruvate is reduced to lactate by lactate dehydrogenase. This oxidises reduced NAD to NAD which can be recycled in glycolysis so a small amount of ATP produced by substrate level phosphorylation.

Question 3

Differences

Answer 3

Hydrogen acceptor is pyruvate vs. ethanal, CO2 only produced in yeast, end products are lactate vs. ethanol, different enzymes involved.

Question 4

Why does it produce a lower yield of ATP than aerobic?

Answer 4

No oxidative phosphorylation as no oxygen as final e- acceptor and no ETC. Not enough recycling of NAD so Krebs and Link reactions stop.

Question 5

Advantages

Answer 5

Glycolysis can still continue as small amounts of NAD recycled so small amounts of ATP produced by substrate level phosphorylation.