When pyruvate is used to form acetyl CoA, the product has only two carbon atoms. What happened to the third carbon?

Pyruvate decarboxylation is a crucial metabolic process that occurs in the mitochondria, where pyruvate, a three-carbon compound derived from glucose, is converted into acetyl CoA, a two-carbon molecule. During this reaction, one carbon atom is removed from pyruvate in the form of carbon dioxide (CO2), which is released as a byproduct. This step is essential for linking glycolysis to the citric acid cycle.

Acetyl CoA is a central metabolite in cellular respiration, formed from the decarboxylation of pyruvate. It serves as a key substrate for the citric acid cycle, where it combines with oxaloacetate to form citrate, initiating a series of reactions that produce energy. Acetyl CoA is also involved in fatty acid synthesis and other metabolic pathways, highlighting its importance in energy metabolism.

The loss of carbon during metabolic processes, such as the conversion of pyruvate to acetyl CoA, is a common occurrence in cellular respiration. This loss typically manifests as carbon dioxide, which is a waste product of aerobic respiration. Understanding this concept is vital for grasping how organisms convert food into energy while also regulating carbon balance in biological systems.