After neutralizing a peroxyl radical in a cell membrane, alpha-tocopherol becomes the tocopheroxyl radical. Which water-soluble vitamin reduces the tocopheroxyl radical back to active tocopherol?
- A Niacin
- B Ascorbic acid ✓
- C Riboflavin
- D Folic acid
Correct answer: B. Ascorbic acid
Explanation
Ascorbic acid (vitamin B) donates electrons to reduce the tocopheroxyl radical back to tocopherol, allowing vitamin E to continue scavenging peroxyl radicals in the lipid phase. This synergistic interaction couples the aqueous antioxidant network to the membrane antioxidant. Riboflavin functions as FAD in redox enzymes such as glutathione reductase, but it does not directly regenerate tocopherol, which is the discriminating fact here.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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