What happens during the transition reaction from glycolysis to the Krebs cycle?

During the transition reaction from glycolysis to the Krebs cycle, pyruvate, which is produced from glycolysis, undergoes a series of transformations to become Acetyl-CoA. This step is crucial as it effectively links the anaerobic processes of glycolysis, occurring in the cytoplasm, to the aerobic processes of the Krebs cycle, taking place in the mitochondria.

In this transition reaction, each molecule of pyruvate (which is a three-carbon compound) is decarboxylated, meaning one carbon is removed in the form of carbon dioxide (CO2), resulting in a two-carbon molecule. This process also involves the reduction of NAD+ to NADH, capturing energy in the form of a high-energy electron carrier. The remaining two-carbon molecule then combines with coenzyme A, forming Acetyl-CoA, which is a key substrate that enters the Krebs cycle, where it will be further oxidized for energy production.

Understanding this process highlights the importance of Acetyl-CoA as it acts as a crucial metabolic hub, feeding into the Krebs cycle, which is vital for producing ATP and other electron carriers needed for cellular respiration.