What is the primary reaction that connects glycolysis to the Krebs cycle?

The primary reaction that connects glycolysis to the Krebs cycle is known as the link reaction, or pyruvate decarboxylation. In this step, each molecule of pyruvate produced during glycolysis is transported into the mitochondria, where it undergoes a series of transformations.

During the link reaction, pyruvate is converted into acetyl-CoA, which is a crucial substrate that enters the Krebs cycle. This conversion involves the removal of a carbon dioxide molecule and the reduction of NAD+ to form NADH. Acetyl-CoA then combines with oxaloacetate to initiate the Krebs cycle, which subsequently produces more NADH and FADH2 that are essential for the electron transport chain.

Other options refer to processes that are involved either before or after the Krebs cycle. For instance, the conversion of glucose to pyruvate describes glycolysis itself, while oxidative phosphorylation occurs after the Krebs cycle as part of cellular respiration, where the NADH and FADH2 generated are used to produce ATP. Fermentation occurs in anaerobic conditions and is an alternative pathway to produce energy when oxygen is not present but does not link glycolysis to the Krebs cycle. Thus, the link reaction serves as the crucial bridge connecting the