Question

Assertion :Reduced coenzyme formed in the oxidation of isocitric acid accounts for more ATP production in electron transport than the reduced coenzyme formed in succinic acid oxidation. Reason: In the reoxidation of mitochondrial NADH, the number of protons translocated from matrix to intermembrane space is less than the protons translocated when FADH${}_2$ is oxidized.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

• Isocitric acid is the intermediate of Kreb's cycle. In oxidation of isocitric acid, it is converted to oxalosuccinic acid in the presence of isocitrate dehydrogenase and produces one molecule of NADH.
• One molecule of NADH is equivalent to 3 ATP whereas, in case of oxidation in succinic acid, succinic acid is converted to fumaric acid in the presence of enzyme succinate dehydrogenase to form FADH.
• One molecule of FADH is equivalent to 2 ATP.
• Reoxidation of 1 NADH releases 2 electrons and 1 protons, while reoxidation of FADH${}_2$ releases 2 electrons and 2 protons which are pumped into the intermembrane space, therefore, reason is true.

Thus, the correct answer is option B.