Final answer:
The transition from glycolysis to the citric acid cycle involves the conversion of pyruvate into acetyl CoA by pyruvate dehydrogenase. Acetyl CoA then enters the citric acid cycle, where it participates in a series of reactions to produce ATP, NADH, and FADH2.
Step-by-step explanation:
The transition from glycolysis to the citric acid cycle involves the conversion of pyruvate, the product of glycolysis, into a two-carbon acetyl group. This conversion is carried out by the enzyme complex pyruvate dehydrogenase in a process called the transition reaction. During the transition reaction, pyruvate is first decarboxylated, resulting in the release of carbon dioxide and the formation of acetyl CoA. Acetyl CoA then enters the citric acid cycle, where it combines with a four-carbon molecule to form citrate, initiating a series of enzyme-catalyzed reactions that ultimately generate high-energy molecules such as ATP, NADH, and FADH2.