Which micronutrient is a powerful antioxidant that helps to prevent damage to cell membranes?

Question

BlackTom AI · Accepted Answer

Vitamin E is a lipid-soluble antioxidant that protects cell membranes from oxidative damage.

1. Relevant knowledge points and concepts
- Cell membranes contain polyunsaturated fatty acids (PUFAs) that are susceptible to free radical attack (lipid peroxidation).
- Antioxidants interrupt chain reactions of lipid peroxidation by neutralizing lipid peroxyl radicals.
- Vitamin E refers to a family of tocopherols and tocotrienols; it is fat-soluble and locates within membranes where it can protect lipids.
- Other listed micronutrients have distinct roles (enzyme cofactors, bone metabolism, blood clotting, one‑carbon metabolism) rather than primary membrane antioxidant protection.

2. Step-by-step reasoning
- Oxidative stress produces reactive oxygen species that abstract hydrogen from PUFAs, creating lipid radicals.
- Lipid radicals react with oxygen to form lipid peroxyl radicals, propagating damage.
- Vitamin E donates a hydrogen atom to lipid peroxyl radicals, converting them into more stable lipid hydroperoxides and stopping the chain reaction.
- The vitamin E radical formed is relatively stable and can be recycled back to active form by water‑soluble antioxidants (e.g., vitamin C).

3. Calculations
- No numerical calculations are required for this conceptual question.

4. Why the correct answer is correct
- Because vitamin E’s chemical properties (lipid solubility and H‑donating ability) position it ideally to scavenge peroxyl radicals in membrane lipids, preventing damage to cell membranes.

5. Why other options are incorrect (brief)
- Chromium: trace element involved in insulin signaling, not a membrane antioxidant.
- Vitamin D: regulates calcium and bone metabolism, immune modulation; not a primary antioxidant.
- Folate: one‑carbon metabolism and nucleotide synthesis; not an antioxidant for membranes.
- Vitamin B12: methylation and red blood cell formation; not a membrane antioxidant.
- Vitamin K: required for γ‑carboxylation of clotting factors; not an antioxidant protecting membranes.
- Magnesium: an essential mineral and enzyme cofactor, not a primary membrane antioxidant.

6. Conclusion
- The correct answer is Vitamin E, matching the provided answer.

Which micronutrient is a powerful antioxidant that helps to prevent damage to cell membranes?单项选择题

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