What end product is formed in the Krebs cycle?

The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, primarily functions to oxidize acetyl-CoA to produce energy-rich molecules. One of the key end products of this cycle, which takes place in the mitochondria, is NADH.

Throughout the Krebs cycle, acetyl-CoA combines with oxaloacetate to form citrate, which undergoes a series of enzymatic reactions. During these reactions, electron carriers like NAD+ are reduced to NADH. This process is significant because NADH plays a crucial role in cellular respiration, especially in the electron transport chain, where it is utilized to generate ATP, the primary energy currency of the cell.

While compounds like glucose and acetyl-CoA are involved in earlier stages or processes, such as glycolysis and the breakdown of carbohydrates into pyruvate that can then convert into acetyl-CoA, they are not the direct end products of the Krebs cycle itself. Citrate is an intermediate product of the cycle but not an end product. Thus, NADH is the correct answer as it represents one of the primary outputs that carry the high-energy electrons harvested during the cycle, which are essential for ATP production.