Fates of Pyruvate

Pyruvate, the end product of glycolysis, can have several metabolic fates depending on the physiological conditions inside the organism.

Under aerobic conditions, pyruvate is converted into acetyl-coenzyme A, which is then channeled through the TCA cycle and the electron transport chain to produce energy in the form of ATP.

But, under anaerobic conditions, the electron transport chain does not function, as seen in yeast and anaerobic bacteria. So, pyruvate is fermented into ethanol while oxidizing NADH into NAD+ . NAD+ is then recycled back to glycolysis.

In most vertebrates, temporary low oxygen conditions trigger another form of pyruvate fermentation, where it is fermented into lactate, producing NAD+.

The regeneration of NAD+ during fermentation helps cells to continue making ATP even in low-oxygen conditions via glycolysis.

During low blood glucose levels, pyruvate can also be converted back to glucose 6-phosphate by a process called gluconeogenesis. Glucose 6-phosphate is then converted into glucose, which restores the blood glucose level.