Question

Q13). Although pyruvate is the end product of glycolysis and no more ATP is generated by fermentation of pyruvate to ethanol, yeast produce ethanol under anaerobic conditions because

A) pyruvate export requires more energy than ethanol export.

B) pyruvate to ethanol fermentation decreases deleterious CO2 levels.

C) glycolysis substrate-level phosphorylation changes pyruvate to ethanol.

D) transfer of electrons from NADH to pyruvate to make ethanol regenerates NAD+, which is necessary for new rounds of glycolysis to proceed.

Answer 1

Yeast produce ethanol under anaerobic conditions to regenerate NAD+ from NADH, allowing ongoing ATP production through glycolysis.

Step-by-step explanation:

Yeast produce ethanol under anaerobic conditions because transfer of electrons from NADH to pyruvate to make ethanol regenerates NAD+, which is necessary for new rounds of glycolysis to proceed. During alcoholic fermentation, pyruvate, which is the end product of glycolysis, is converted to ethanol and carbon dioxide.

This process is crucial as it regenerates NAD+ from NADH, allowing the cell to continue producing ATP in the absence of oxygen through glycolysis. Although no ATP is generated directly from the fermentation process, the continuation of glycolysis yields a net of two ATP molecules per glucose molecule fermented.