CSSD Practice Exam 2025 – Complete Study Resource

Acetyl CoA is a central molecule in aerobic metabolism, primarily functioning as a key substrate for the Krebs cycle, also known as the citric acid cycle. During this cycle, acetyl CoA combines with oxaloacetate to form citrate, initiating a series of enzymatic reactions that produce important energy carriers such as NADH and FADH2. These carriers are crucial for the subsequent production of ATP through the electron transport chain, which occurs in the mitochondria.

In contrast to the other options, acetyl CoA does not initiate anaerobic respiration, as that process is primarily dependent on the absence of oxygen and utilizes glucose directly. While it can assist in fat breakdown as it is derived from fatty acids during their catabolism, this role is secondary compared to its central function in the Krebs cycle. Acetyl CoA does not overload the glycolytic pathway; rather, it is the end product of glycolysis and other metabolic pathways, indicating a more structured and balanced metabolic flow. Thus, the importance of acetyl CoA lies predominantly in its direct entry into the Krebs cycle, facilitating ATP production in the presence of oxygen.