Advanced Placement (AP) Biology Practice Exam

What is the role of pyruvate dehydrogenase?

1. Converting lactic acid to glucose

2. Converting pyruvate to acetyl-CoA

3. Generating ATP from acetyl-CoA

4. Breaking down fatty acids

The correct answer is: Converting pyruvate to acetyl-CoA

Pyruvate dehydrogenase plays a crucial role in cellular respiration by catalyzing the conversion of pyruvate, which is produced during glycolysis, into acetyl-CoA. This reaction is significant because it links the glycolytic pathway to the citric acid cycle (Krebs cycle). Once pyruvate is transported into the mitochondria, the pyruvate dehydrogenase complex facilitates this decarboxylation process, releasing carbon dioxide and reducing NAD+ to NADH in the process. Acetyl-CoA then enters the citric acid cycle, where it can be further oxidized to generate ATP and other high-energy electron carriers, ultimately contributing to the production of ATP through oxidative phosphorylation. This function of pyruvate dehydrogenase is essential for efficient energy production in aerobic organisms, making it a pivotal enzyme in metabolism.