Which molecule acts as a coenzyme during the Krebs cycle?

• A. NAD+
• B. FADH2
• C. Coenzyme A
• D. ATP

Answer: (C)

The correct answer is Coenzyme A. In the Krebs cycle, also known as the citric acid cycle, Coenzyme A plays a crucial role in the formation of acetyl-CoA, which enters the cycle. Acetyl-CoA is derived from the metabolism of carbohydrates, fats, and proteins and is essential for the initiation of the cycle. Coenzyme A serves as a carrier of acyl groups, enabling the transfer of acetyl groups to oxaloacetate to form citrate, thereby facilitating the continuation of metabolic processes.

While NAD+ and FADH2 are important molecules in the Krebs cycle as well, they act as electron carriers rather than coenzymes. NAD+ is reduced to NADH, and FAD is reduced to FADH2 during various steps of the Krebs cycle, but they do not assist in the formation of acetyl-CoA. ATP, on the other hand, is the primary energy currency of the cell and is produced in various cellular processes, but it does not serve as a coenzyme during the cycle. Thus, Coenzyme A is recognized specifically for its coenzyme function in the Krebs cycle, particularly in the activation and transfer of acetyl groups.