Which substance must be generated from glycolysis for the citric acid cycle to occur?

The citric acid cycle, also known as the Krebs cycle, requires acetyl CoA to proceed. This molecule is generated from pyruvate, which is the end product of glycolysis. When glucose is broken down through glycolysis, it results in two molecules of pyruvate. For these pyruvate molecules to enter the citric acid cycle, they must be converted into acetyl CoA in a reaction that takes place within the mitochondria. This conversion is crucial because the acetyl CoA then enters the citric acid cycle, where it participates in a series of reactions that produce energy carriers such as NADH and FADH2, which are essential for ATP production in cellular respiration.

While pyruvate is produced during glycolysis, it is not directly involved in the citric acid cycle; it requires conversion to acetyl CoA first. Glucose is the initial substrate that enters the glycolytic pathway but is not a product of glycolysis itself. Fatty acids, on the other hand, are typically involved in the process of beta-oxidation rather than glycolysis and the citric acid cycle.