Final answer:
Pyruvate undergoes oxidative decarboxylation to form acetyl CoA before entering the Krebs cycle. This process includes the release of CO2 and the formation of NADH. The Krebs cycle produces ATP, NADH, and FADH2, important for oxidative phosphorylation.
Step-by-step explanation:
As pyruvate is prepared for the citric acid cycle, it undergoes a process of oxidative decarboxylation. During this process, the three-carbon pyruvate molecule generated during glycolysis is converted into a two-carbon acetyl coenzyme A (acetyl CoA) molecule. This reaction, catalyzed by the enzyme pyruvate dehydrogenase, releases one carbon dioxide molecule and transfers electrons to NAD* to form NADH. The resulting acetyl CoA then enters the Krebs cycle by combining with oxaloacetate to form citrate, while the coenzyme A is released and recycled.
The Krebs cycle involves a series of redox, dehydration, hydration, and decarboxylation reactions, which result in the production of two carbon dioxide molecules from each acetyl group. During these reactions, there is also a small amount of ATP synthesized by substrate-level phosphorylation. Moreover, a number of reduced electron carriers, specifically NADH and FADH2, are generated, which will later be used in the production of ATP through oxidative phosphorylation.