Which of the following processes produces the most ATP molecules per glucose molecule consumed? Explain briefly and choose correct from the option
a. Citric Acid Cycle.
b. electron transport chain.
c. glycolysis.
The Correct Answer and Explanation is :
The correct answer is: b. Electron transport chain (ETC).
Explanation:
The electron transport chain (ETC) produces the most ATP molecules per glucose molecule consumed during cellular respiration. Here’s a breakdown of why this is the case:
- Overview of Cellular Respiration:
Cellular respiration consists of three main stages:
- Glycolysis: Occurs in the cytoplasm and breaks down one glucose molecule into two pyruvate molecules, producing a net gain of 2 ATP and 2 NADH molecules.
- Citric Acid Cycle (Krebs Cycle): Occurs in the mitochondrial matrix, producing 2 ATP (via substrate-level phosphorylation), along with NADH and FADH₂ molecules that are crucial for the ETC.
- Electron Transport Chain (ETC): Takes place in the inner mitochondrial membrane, where NADH and FADH₂ donate electrons. This drives the creation of a proton gradient, which powers ATP synthesis via oxidative phosphorylation.
- ATP Production by Each Stage:
- Glycolysis: Net gain of 2 ATP.
- Citric Acid Cycle: Produces 2 ATP directly, but generates 6 NADH and 2 FADH₂, which are used in the ETC.
- ETC: Uses NADH and FADH₂ to drive oxidative phosphorylation, generating approximately 28–34 ATP per glucose molecule.
- Why the ETC Produces the Most ATP:
- Each NADH molecule contributes enough energy to generate about 2.5 ATP, while each FADH₂ produces approximately 1.5 ATP.
- The ETC is highly efficient due to the coupling of electron transfer to proton pumping, which drives ATP synthase.
- Conclusion:
While glycolysis and the citric acid cycle contribute to ATP production, the ETC generates the bulk of ATP because it leverages the energy stored in NADH and FADH₂. Therefore, the ETC is the most significant ATP-producing process in cellular respiration.