Question

Name the connecting link between glycolysis and TCA cycle and explain it.

Answer 1

The connecting link between glycosis and TCA cycle is Acetylation of pyruvate.
Link reaction or acytylation of pyruvate: Pyruvic acid undergoes oxidative decarboxylation before entering Krebs cycle. Removal of carbon dioxide along with oxidation by removal of 2H⁺ takes place. The reaction is catalyzed by enzyme pyruvic dehydrogenase (oxidase). Co-enzyme NAD and co-enzyme –A, are required for this reaction. Pyruvic acid (3C) undergoes decarboxylation first and then oxidation by removal of 2H⁺, which is taken up by NAD and NADH₂ is formed. Acetyl fraction (2C) that remains after decarboxylation is taken up by co-enzyme A and Acetyl Co-A is formed. This is called Acetylation of pyruvate.
Glycolysis ends with the formation of pyruvate and after acetylation enters as acetyl Co-A in the Kerbs cycle. Therefore, formation of acetyl Co-A or acetylation of pyruvate is called connecting link between glycolysis and Krebs cycle to link reaction. Pyruvate is converted to acetyl coenzyme-A in the perimitochondiral space. The whole process can be represented as follows.