Acetyl Coenzyme A: Strategic Intermediate in Respiration

In aerobic metabolism the two molecules of pyruvic acid formed during glycolysis enter a mitochondrion. There, each molecule is oxidized, and one of the carbons is released as carbon dioxide (Figure 4-12). The 2-carbon residue condenses with coenzyme A to form acetyl coenzyme A (acetyl-CoA).

Pyruvic acid is the undissociated form of the acid . Under physiological conditions pyruvic acid typically dissociates into pyruvaye and H⁺. It is correct to use either term in describing this and other organic acids (such as lactic acid, or lactate) in metabolism.

Acetyl coenzyme A is a critically important compound. Its oxidation in the Krebs cycle (following) provides energized electrons to generate ATP, and it is a crucial intermediate in lipid metabolism.