Question

Identify how many carbons from one glucose molecule enter one round of the Krebs cycle

Answer 1

Two carbons from one glucose molecule enter one round of the Krebs cycle in the form of an acetyl group, derived from a three-carbon pyruvate transformed into acetyl-CoA after glycolysis. This process occurs twice for one glucose molecule because glycolysis produces two pyruvates.

Step-by-step explanation:

The question pertains to the Krebs cycle and its relation to glucose metabolism. During one round of the Krebs cycle, two carbons from one glucose molecule enter the cycle. This is because glucose, a six-carbon molecule, is initially broken down through glycolysis into two three-carbon pyruvate molecules. Each pyruvate is then converted into a two-carbon acetyl group, which combines with coenzyme A to form acetyl-CoA. This is a crucial step known as the oxidative decarboxylation of pyruvate, during which one carbon from each pyruvate is released as carbon dioxide. Therefore, two acetyl-CoA molecules are generated from one glucose molecule, and each acetyl-CoA enters the Krebs cycle separately. Each turn of the Krebs cycle processes one acetyl-CoA, producing two molecules of CO₂, three molecules of NADH, one molecule of FADH₂, and one molecule of ATP (or GTP).

Answer 2

The answer is, all three carbons from glucose molecules enters the Kreb cycle. But three at a time only. One molecule is broken down to two pyruvate molecules and then used in Krebs cycle. Which means that one glucose molecules leads to two cycles of the Kreb cycle with three carbons going to the cycle at one time.