Cell injury and adaptation: radiation injury: 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 and adaptation: radiation injury

Sample item

A child receiving therapeutic ionising radiation develops damage to rapidly dividing cells in the irradiated field. What is the principal mechanism by which the radiation injures cells?

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

The answer and the reasoning

B. Radiolysis of water generating hydroxyl radicals that damage DNA

Ionising radiation splits intracellular water into free radicals, especially the hydroxyl radical, which damages DNA, proteins and lipids. DNA breaks activate p53 and can lead to cell cycle arrest or apoptosis, so rapidly dividing tissues are most sensitive. Direct DNA ionisation also contributes.

Option by option

  • A. Direct inhibition of cytochrome oxidase in the electron transport chain

    Cytochrome oxidase inhibition is the effect of cyanide poisoning.

  • B. Radiolysis of water generating hydroxyl radicals that damage DNA (correct)

    Correct. Water radiolysis produces free radicals that break DNA strands.

  • C. Opening of calcium channels in the sarcoplasmic reticulum

    Calcium channel opening is not the way radiation damages cells.

  • D. Antibody binding to cell surface antigens

    Antibody binding drives immune injury and is not a radiation mechanism.

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 B, Radiolysis of water generating hydroxyl radicals that damage DNA. Ionising radiation splits intracellular water into free radicals, especially the hydroxyl radical, which damages DNA, proteins and lipids.

Why is "Direct inhibition of cytochrome oxidase in the electron transport cha…" not the answer?

Cytochrome oxidase inhibition is the effect of cyanide poisoning.

Why is "Opening of calcium channels in the sarcoplasmic reticulum" not the answer?

Calcium channel opening is not the way radiation damages cells.

Why is "Antibody binding to cell surface antigens" not the answer?

Antibody binding drives immune injury and is not a radiation mechanism.

What concept does this question test?

It tests Cell injury and adaptation: radiation injury in Pathology. DNA breaks activate p53 and can lead to cell cycle arrest or apoptosis, so rapidly dividing tissues are most sensitive. Direct DNA ionisation also contributes.

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 Cell injury and adaptation: radiation injury?

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.