"After glycolysis, the fate of pyruvate depends on whether or not the cell has access to oxygen. Discuss the potential fates of pyruvate in the presence and absence of oxygen."

Fate of pyruvate in the presence of oxygen:

-conversion to oxaloacetate by pyruvate carboxylase (biotin).

-conversion to Acetyl-CoA by Pyruvate dehydrogenase.

Fate of pyruvate in the absence of oxygen:

-conversion to lactate by lactic acid dehydrogenase.

Explanation:

Oxaloacetate can replenish the TCA cycle intermediates and be used as a substrate for gluconeogenesis.

Acetyl-CoA, which is formed by oxidative decarboxylation of pyruvate by the pyruvate dehydrogenase complex, is a major fuel used in the TCA cycle. Acetyl-CoA is also a building block for fatty acid synthesis.

Lactate, formed by the action of lactate dehydrogenase, is the final product of anaerobic glycolysis in eukaryotic cells. The formation of lactate is the major fate for pyruvate in the lens and cornea of the eye, kidney medulla, testes, leukocytes, and red blood cells, because these are all poorly vascularized and/or lack mitochondria.