Exemplar Problems

Question:

Explain the fate of pyruvate generated during glycolysis under aerobic and anaerobic conditions.

Answer:

• Under aerobic conditions (presence of oxygen), pyruvate is further oxidized in the mitochondria through the citric acid cycle (Krebs cycle) and the electron transport chain, leading to the production of a significant amount of ATP. In this case, pyruvate is converted into acetyl-CoA before entering the citric acid cycle.

  • Under anaerobic conditions (absence of oxygen or low oxygen), pyruvate can undergo fermentation to regenerate NAD+ and allow glycolysis to continue. Depending on the organism, this may result in lactic acid fermentation (e.g., in muscle cells) or alcoholic fermentation (e.g., in yeast cells), with the production of lactic acid or ethanol, respectively.