Cell injury and adaptation: annexin V detection of apoptosis: 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: annexin V detection of apoptosis

Sample item

In flow cytometry of a culture exposed to a cytotoxic drug, one population of cells binds annexin V but excludes propidium iodide. Which state are these cells in?

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

The answer and the reasoning

B. Early apoptosis with intact membrane

Early in apoptosis, phosphatidylserine flips from the inner to the outer leaflet of the plasma membrane, where annexin V binds it. The membrane is still intact, so propidium iodide is excluded. Cells that stain with both have lost membrane integrity, as in late apoptosis or necrosis.

Option by option

  • A. Quiescence in the G0 phase

    Quiescent cells do not expose phosphatidylserine.

  • B. Early apoptosis with intact membrane (correct)

    Correct. Surface phosphatidylserine with an intact membrane marks early apoptosis.

  • C. Viable cells with normal membrane

    Viable cells keep phosphatidylserine inside and do not bind annexin V.

  • D. Late necrosis with ruptured membrane

    Ruptured membranes would admit propidium iodide, so these cells would stain with both dyes.

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, Early apoptosis with intact membrane. Early in apoptosis, phosphatidylserine flips from the inner to the outer leaflet of the plasma membrane, where annexin V binds it.

Why is "Quiescence in the G0 phase" not the answer?

Quiescent cells do not expose phosphatidylserine.

Why is "Viable cells with normal membrane" not the answer?

Viable cells keep phosphatidylserine inside and do not bind annexin V.

Why is "Late necrosis with ruptured membrane" not the answer?

Ruptured membranes would admit propidium iodide, so these cells would stain with both dyes.

What concept does this question test?

It tests Cell injury and adaptation: annexin V detection of apoptosis in Pathology. The membrane is still intact, so propidium iodide is excluded. Cells that stain with both have lost membrane integrity, as in late apoptosis or necrosis.

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 Cell injury and adaptation: annexin V detection of apoptosis?

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.