Cytosolic NADH generated during glycolysis cannot cross the inner mitochondrial membrane directly. In skeletal muscle and brain, where the glycerol-3-phosphate shuttle operates, what is the ATP yield per cytosolic NADH reoxidized?
- A 2.5 ATP
- B 2.0 ATP
- C 1.5 ATP ✓
- D 1.0 ATP
Correct answer: C. 1.5 ATP
Explanation
The glycerol-3-phosphate shuttle transfers electrons from cytosolic NADH to mitochondrial FAD via the inner-membrane glycerol-3-phosphate dehydrogenase, producing FADH2 that feeds Complex II. FADH2 oxidation yields approximately 1.5 ATP because it bypasses Complex I. The malate-aspartate shuttle used in liver, heart, and kidney transfers electrons to mitochondrial NAD+, giving 2.5 ATP per cytosolic NADH.
Reference: Lehninger Principles of Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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