Which molecules enter the Citric Acid Cycle?

Acetyl-CoA is the primary molecule that enters the Citric Acid Cycle (CAC), also known as the Krebs cycle or TCA cycle. This molecule is derived from the breakdown of carbohydrates, fats, and proteins during cellular respiration. Once it enters the cycle, Acetyl-CoA combines with oxaloacetate to form citrate, which is the first step of the cycle.

Acetyl-CoA serves as a crucial entry point for the carbon atoms required in the cycle, facilitating the subsequent series of reactions that lead to the production of energy-rich molecules such as NADH, FADH2, and GTP, as well as the regeneration of oxaloacetate, which is necessary for the cyclical nature of this metabolic pathway. Understanding the role of Acetyl-CoA is fundamental to grasping how energy is extracted from various substrates during cellular respiration.