Toxicology: cyanogenic glycosides: practice question

A Forensic Medicine 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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Forensic Medicine · Toxicology: cyanogenic glycosides

Sample item

A child eats a large number of bitter apricot kernels and soon develops breathlessness, headache and collapse, with a bitter almond smell on the breath and bright red venous blood. What is the toxic agent?

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

The answer and the reasoning

D. Cyanide released from amygdalin in the gut

Bitter apricot kernels, bitter almonds and poorly processed cassava contain cyanogenic glycosides such as amygdalin, which are hydrolysed in the gut to release hydrogen cyanide. Cyanide blocks cytochrome oxidase, so tissues cannot use oxygen and venous blood stays bright red. Treatment includes hydroxocobalamin or sodium nitrite with sodium thiosulphate.

Option by option

  • A. Atropine in the kernels

    Atropine is from Atropa and Datura and gives dry skin and dilated pupils, not bright red venous blood.

  • B. Colchicine in the kernels

    Colchicine is in Gloriosa and Colchicum, not in apricot kernels.

  • C. Abrin released from the kernels

    Abrin is found in Abrus seeds and not in apricot kernels.

  • D. Cyanide released from amygdalin in the gut (correct)

    Correct. Amygdalin releases cyanide, which blocks cytochrome oxidase.

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 Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is D, Cyanide released from amygdalin in the gut. Bitter apricot kernels, bitter almonds and poorly processed cassava contain cyanogenic glycosides such as amygdalin, which are hydrolysed in the gut to release hydrogen cyanide.

Why is "Atropine in the kernels" not the answer?

Atropine is from Atropa and Datura and gives dry skin and dilated pupils, not bright red venous blood.

Why is "Colchicine in the kernels" not the answer?

Colchicine is in Gloriosa and Colchicum, not in apricot kernels.

Why is "Abrin released from the kernels" not the answer?

Abrin is found in Abrus seeds and not in apricot kernels.

What concept does this question test?

It tests Toxicology: cyanogenic glycosides in Forensic Medicine. Cyanide blocks cytochrome oxidase, so tissues cannot use oxygen and venous blood stays bright red. Treatment includes hydroxocobalamin or sodium nitrite with sodium thiosulphate.

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 Toxicology: cyanogenic glycosides?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine 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.