What determines the fate of pyruvate?

The fate of pyruvate is primarily determined by the availability of oxygen. In the presence of oxygen, pyruvate is converted into acetyl-CoA for the citric acid cycle and oxidative phosphorylation, which generates large amounts of ATP. In the absence of oxygen, pyruvate undergoes fermentation: it is converted to lactate in muscle cells (lactic acid fermentation) or to ethanol and CO2 in yeast (alcoholic fermentation). Additionally, factors such as cellular energy needs and enzyme activity also influence pyruvate’s fate.