General physiology: extrinsic apoptosis: practice question

A Physiology 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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Physiology · General physiology: extrinsic apoptosis

Sample item

A cytotoxic T cell binds Fas ligand on its surface to Fas on a virus-infected cell, and the target dies by apoptosis without mitochondrial involvement as the first step. Which initiator caspase is activated by the death receptor complex?

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

The answer and the reasoning

C. Caspase-8

Death receptors such as Fas recruit adaptor proteins that activate initiator caspase-8, which then activates executioner caspases. The intrinsic pathway instead releases cytochrome c from mitochondria and activates caspase-9 through the apoptosome.

Option by option

  • A. Caspase-1

    Caspase-1 is an inflammatory caspase, not an apoptotic initiator.

  • B. Caspase-3

    Caspase-3 is an executioner caspase activated downstream of the initiators.

  • C. Caspase-8 (correct)

    Correct. Caspase-8 is the initiator of the extrinsic death receptor pathway.

  • D. Caspase-9

    Caspase-9 is the initiator of the intrinsic mitochondrial pathway.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Caspase-8. Death receptors such as Fas recruit adaptor proteins that activate initiator caspase-8, which then activates executioner caspases.

Why is "Caspase-1" not the answer?

Caspase-1 is an inflammatory caspase, not an apoptotic initiator.

Why is "Caspase-3" not the answer?

Caspase-3 is an executioner caspase activated downstream of the initiators.

Why is "Caspase-9" not the answer?

Caspase-9 is the initiator of the intrinsic mitochondrial pathway.

What concept does this question test?

It tests General physiology: extrinsic apoptosis in Physiology. The intrinsic pathway instead releases cytochrome c from mitochondria and activates caspase-9 through the apoptosome.

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 General physiology: extrinsic apoptosis?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.