Cell injury: Fenton reaction and iron: practice question

A Pathology 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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Pathology · Cell injury: Fenton reaction and iron

Sample item

A 16-year-old with beta-thalassaemia major on regular transfusions without chelation develops cardiac dysfunction. Free iron in the myocardium is thought to damage cells by generating the most reactive oxygen species. Which reaction is responsible?

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

The answer and the reasoning

C. Reduction of hydrogen peroxide by ferrous iron, producing the hydroxyl radical

In the Fenton reaction, Fe2+ donates an electron to hydrogen peroxide to yield the hydroxyl radical and Fe3+. The hydroxyl radical is the most damaging reactive oxygen species and attacks lipids, proteins and DNA. Iron overload therefore injures the heart, liver and endocrine glands, and chelation limits this.

Option by option

  • A. Reduction of hydrogen peroxide to water by glutathione peroxidase

    Glutathione peroxidase is a detoxifying step that removes peroxide rather than creating radicals.

  • B. Dismutation of two superoxide anions to hydrogen peroxide

    Superoxide dismutation produces hydrogen peroxide, a less reactive species, and needs no iron.

  • C. Reduction of hydrogen peroxide by ferrous iron, producing the hydroxyl radical (correct)

    Correct. The Fenton reaction links free iron to hydroxyl radical formation.

  • D. Conversion of hydrogen peroxide to hypochlorous acid by myeloperoxidase

    Myeloperoxidase makes hypochlorous acid in neutrophils and does not produce the hydroxyl radical.

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 Pathology question

What is the answer to this Pathology question?

The best answer is C, Reduction of hydrogen peroxide by ferrous iron, producing the hydroxyl radical. In the Fenton reaction, Fe2+ donates an electron to hydrogen peroxide to yield the hydroxyl radical and Fe3+.

Why is "Reduction of hydrogen peroxide to water by glutathione peroxidase" not the answer?

Glutathione peroxidase is a detoxifying step that removes peroxide rather than creating radicals.

Why is "Dismutation of two superoxide anions to hydrogen peroxide" not the answer?

Superoxide dismutation produces hydrogen peroxide, a less reactive species, and needs no iron.

Why is "Conversion of hydrogen peroxide to hypochlorous acid by myeloperoxida…" not the answer?

Myeloperoxidase makes hypochlorous acid in neutrophils and does not produce the hydroxyl radical.

What concept does this question test?

It tests Cell injury: Fenton reaction and iron in Pathology. The hydroxyl radical is the most damaging reactive oxygen species and attacks lipids, proteins and DNA. Iron overload therefore injures the heart, liver and endocrine glands, and chelation limits this.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Cell injury: Fenton reaction and iron?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.