Final answer:
Pyruvic acid is transported into the mitochondria, where it is converted into acetyl CoA via the enzyme pyruvate dehydrogenase. This step precedes the Krebs cycle, where acetyl CoA is further broken down to generate energy.
Step-by-step explanation:
Pyruvic acid enters the mitochondria and is first converted into acetyl CoA. This process occurs in the mitochondrial matrix where the enzyme pyruvate dehydrogenase catalyzes the conversion of pyruvate into acetyl CoA, releasing a molecule of carbon dioxide and forming NADH from NAD+ in a reaction known as oxidative decarboxylation. After its formation, acetyl CoA then enters the Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, where it is metabolized to produce ATP, NADH, and FADH2.
The three-carbon pyruvate molecule generated during glycolysis moves from the cytoplasm into the mitochondrial matrix, where it is converted by the enzyme pyruvate dehydrogenase into a two-carbon acetyl Coenzyme A (acetyl CoA) molecule. This reaction is an oxidative decarboxylation reaction. It converts the three-carbon pyruvate into a two-carbon acetyl CoA molecule, releasing carbon dioxide and transferring two electrons that combine with NAD* to form NADH. Acetyl CoA enters the Krebs cycle by combining with a four-carbon molecule, oxaloacetate, to form the six-carbon molecule citrate, or citric acid, at the same time releasing the coenzyme A molecule.