Radiation safety and radiobiology: water radiolysis: practice question

A Radiology 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.

Try it

Radiology · Radiation safety and radiobiology: water radiolysis

Sample item

With sparsely ionising radiation such as X-rays, most DNA damage arises indirectly. Which product of water radiolysis is chiefly responsible?

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

The answer and the reasoning

B. The hydroxyl free radical

X-rays ionise water in the cell to produce highly reactive species, the most damaging being the hydroxyl radical. It attacks DNA bases and the sugar-phosphate backbone within a very short distance. This indirect action explains the protective effect of radical scavengers.

Option by option

  • A. Hydrogen peroxide acting alone

    Peroxide plays a minor role compared with the hydroxyl radical.

  • B. The hydroxyl free radical (correct)

    Correct. The hydroxyl radical mediates most indirect damage.

  • C. Free electrons from the nucleus

    Nuclei do not release electrons in this process.

  • D. Molecular hydrogen gas

    Molecular hydrogen is stable and does not damage DNA.

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.

More Radiology questions

Questions about this Radiology question

What is the answer to this Radiology question?

The best answer is B, The hydroxyl free radical. X-rays ionise water in the cell to produce highly reactive species, the most damaging being the hydroxyl radical.

Why is "Hydrogen peroxide acting alone" not the answer?

Peroxide plays a minor role compared with the hydroxyl radical.

Why is "Free electrons from the nucleus" not the answer?

Nuclei do not release electrons in this process.

Why is "Molecular hydrogen gas" not the answer?

Molecular hydrogen is stable and does not damage DNA.

What concept does this question test?

It tests Radiation safety and radiobiology: water radiolysis in Radiology. It attacks DNA bases and the sugar-phosphate backbone within a very short distance. This indirect action explains the protective effect of radical scavengers.

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 Radiation safety and radiobiology: water radiolysis?

Learn signs with the image, and the disease they point to. Then use the flashcards and the other Radiology 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.