In oxidative phosphorylation (using the modern P/O ratio), approximately how many ATP molecules are generated per mitochondrial NADH oxidized by the electron transport chain?

• A. Approximately 1.5 ATP per NADH
• B. Approximately 4.0 ATP per NADH
• C. Approximately 2.5 ATP per NADH
• D. Approximately 3.0 ATP per NADH

Answer: (C)

Verified step by step guidance

1. Understand that the P/O ratio represents the number of ATP molecules synthesized per atom of oxygen reduced during oxidative phosphorylation.
2. Recall that mitochondrial NADH donates electrons to Complex I of the electron transport chain, which pumps protons across the inner mitochondrial membrane, contributing to the proton motive force used for ATP synthesis.
3. Recognize that the modern P/O ratio for NADH is based on updated measurements of proton pumping and ATP synthase stoichiometry, which estimate the number of ATP molecules produced per NADH oxidized.
4. Use the modern accepted P/O ratio for mitochondrial NADH, which is approximately 2.5 ATP molecules generated per NADH oxidized.
5. Conclude that the correct approximate number of ATP molecules generated per mitochondrial NADH oxidized by the electron transport chain is 2.5 ATP.