Free radicals: vitamin E in membranes: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Free radicals: vitamin E in membranes

Sample item

A premature infant on high oxygen therapy has haemolytic anaemia and a low serum tocopherol level. How does vitamin E protect red cell membranes?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. It donates a hydrogen atom to lipid peroxyl radicals, breaking the chain reaction of peroxidation

Tocopherol is a lipid-soluble chain-breaking antioxidant that gives a hydrogen atom to peroxyl radicals, ending propagation in polyunsaturated membrane lipids. The resulting tocopheroxyl radical is regenerated by vitamin C. Deficiency causes red cell fragility and haemolysis, notably in premature infants.

Option by option

  • A. It reduces hydrogen peroxide to water using glutathione

    Reduction of hydrogen peroxide with glutathione is the function of glutathione peroxidase.

  • B. It chelates iron needed for the Fenton reaction

    Iron chelation is performed by transferrin and ferritin and is not the action of tocopherol.

  • C. It inhibits phospholipase A2 in the membrane

    Phospholipase A2 inhibition is not a mechanism of vitamin E.

  • D. It donates a hydrogen atom to lipid peroxyl radicals, breaking the chain reaction of peroxidation (correct)

    Correct. Chain-breaking donation of hydrogen stops lipid peroxidation spreading.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, It donates a hydrogen atom to lipid peroxyl radicals, breaking the chain reaction of peroxidation. Tocopherol is a lipid-soluble chain-breaking antioxidant that gives a hydrogen atom to peroxyl radicals, ending propagation in polyunsaturated membrane lipids.

Why is "It reduces hydrogen peroxide to water using glutathione" not the answer?

Reduction of hydrogen peroxide with glutathione is the function of glutathione peroxidase.

Why is "It chelates iron needed for the Fenton reaction" not the answer?

Iron chelation is performed by transferrin and ferritin and is not the action of tocopherol.

Why is "It inhibits phospholipase A2 in the membrane" not the answer?

Phospholipase A2 inhibition is not a mechanism of vitamin E.

What concept does this question test?

It tests Free radicals: vitamin E in membranes in Biochemistry. The resulting tocopheroxyl radical is regenerated by vitamin C. Deficiency causes red cell fragility and haemolysis, notably in premature infants.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Free radicals: vitamin E in membranes?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.