What happens to pyruvate if oxygen is present?

When oxygen is present, pyruvate undergoes a critical process where it enters the mitochondria and is converted into Acetyl-CoA. This conversion is an essential step in cellular respiration, linking glycolysis (where pyruvate is produced) to the citric acid cycle (also known as the Krebs cycle).

In the presence of oxygen, the pyruvate dehydrogenase complex catalyzes the decarboxylation of pyruvate, removing one carbon atom as carbon dioxide and reducing NAD+ to NADH in the process. The remaining two-carbon compound is then attached to coenzyme A, forming Acetyl-CoA. This Acetyl-CoA then enters the citric acid cycle, where it is further oxidized for energy production.

The other choices reflect processes that occur under different conditions or in different organisms. Ethanol production occurs during fermentation in anaerobic conditions, while lactate is formed in muscle cells when oxygen levels are low. If pyruvate remains in the cytoplasm, it does not contribute to the aerobic respiration pathway and thus does not optimize energy yield from glucose metabolism. Hence, the transition of pyruvate to Acetyl-CoA in the presence of oxygen is crucial for efficient ATP production