General physiology: intrinsic pathway of 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: intrinsic pathway of apoptosis

Sample item

After severe DNA damage, a cell's mitochondria release a protein into the cytosol that binds Apaf-1 and activates caspase-9, committing the cell to apoptosis. Which protein is released?

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

The answer and the reasoning

A. Cytochrome c

In the intrinsic pathway, mitochondrial outer membrane permeabilisation releases cytochrome c, which forms the apoptosome with Apaf-1 and caspase-9. Bcl-2 opposes this release, while Fas ligand and FADD belong to the extrinsic death-receptor pathway.

Option by option

  • A. Cytochrome c (correct)

    Correct. Cytochrome c with Apaf-1 forms the apoptosome that activates caspase-9.

  • B. Bcl-2

    Bcl-2 is anti-apoptotic and prevents the mitochondrial release.

  • C. Fas ligand

    Fas ligand is a death-receptor ligand of the extrinsic pathway on the cell surface.

  • D. FADD

    FADD is an adaptor of the death receptor complex that activates caspase-8.

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 A, Cytochrome c. In the intrinsic pathway, mitochondrial outer membrane permeabilisation releases cytochrome c, which forms the apoptosome with Apaf-1 and caspase-9.

Why is "Bcl-2" not the answer?

Bcl-2 is anti-apoptotic and prevents the mitochondrial release.

Why is "Fas ligand" not the answer?

Fas ligand is a death-receptor ligand of the extrinsic pathway on the cell surface.

Why is "FADD" not the answer?

FADD is an adaptor of the death receptor complex that activates caspase-8.

What concept does this question test?

It tests General physiology: intrinsic pathway of apoptosis in Physiology. Bcl-2 opposes this release, while Fas ligand and FADD belong to the extrinsic death-receptor pathway.

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 General physiology: intrinsic pathway of 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.