Final answer:
For every glucose molecule that undergoes cellular respiration, two turns of the Krebs cycle occur, resulting in the complete breakdown of the glucose molecule and formation of ATP.
Step-by-step explanation:
For every glucose molecule that undergoes cellular respiration, two turns of the Krebs cycle occur. During the process of glycolysis, one glucose molecule is broken down into two molecules of pyruvate.
Each pyruvate molecule is then converted into an acetyl CoA molecule, which enters the Krebs cycle. Each acetyl CoA results in one turn of the cycle, so since we have two molecules of acetyl CoA generated from one glucose molecule, the Krebs cycle turns twice. Each turn of the cycle produces three NADH molecules, one FADH2 molecule, and one ATP (or GTP) by substrate-level phosphorylation. Consequently, the complete breakdown of one glucose molecule through cellular respiration, including glycolysis, the Krebs cycle, and oxidative phosphorylation, can yield up to 36 molecules of ATP.