Nerve and muscle: SNARE proteins and calcium sensing: 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.

Try it

Physiology · Nerve and muscle: SNARE proteins and calcium sensing

Sample item

At the motor nerve terminal, which protein acts as the calcium sensor that triggers fusion of synaptic vesicles with the plasma membrane?

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

The answer and the reasoning

D. Synaptotagmin

Calcium entering through voltage-gated channels binds synaptotagmin on the vesicle, which triggers the SNARE complex of synaptobrevin, syntaxin and SNAP-25 to complete fusion. Botulinum and tetanus toxins cleave SNARE proteins, preventing release.

Option by option

  • A. Syntaxin

    Syntaxin is a plasma membrane SNARE protein.

  • B. SNAP-25

    SNAP-25 is a plasma membrane SNARE protein.

  • C. Synaptobrevin

    Synaptobrevin is a vesicle SNARE protein and is not the calcium sensor.

  • D. Synaptotagmin (correct)

    Correct. Synaptotagmin senses calcium and triggers fusion.

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 Physiology questions

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is D, Synaptotagmin. Calcium entering through voltage-gated channels binds synaptotagmin on the vesicle, which triggers the SNARE complex of synaptobrevin, syntaxin and SNAP-25 to complete fusion.

Why is "Syntaxin" not the answer?

Syntaxin is a plasma membrane SNARE protein.

Why is "SNAP-25" not the answer?

SNAP-25 is a plasma membrane SNARE protein.

Why is "Synaptobrevin" not the answer?

Synaptobrevin is a vesicle SNARE protein and is not the calcium sensor.

What concept does this question test?

It tests Nerve and muscle: SNARE proteins and calcium sensing in Physiology. Botulinum and tetanus toxins cleave SNARE proteins, preventing release.

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 Nerve and muscle: SNARE proteins and calcium sensing?

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.