Blood and immunity: thrombomodulin: 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 · Blood and immunity: thrombomodulin

Sample item

When thrombin binds thrombomodulin on intact endothelium, its action on the clotting system changes. What does the thrombin-thrombomodulin complex do?

AActivates factor XIII to stabilise fibrinBActivates protein C, which inactivates factors Va and VIIIaCConverts fibrinogen to fibrin at a faster rateDActivates platelets through protease-activated receptors

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

The answer and the reasoning

B. Activates protein C, which inactivates factors Va and VIIIa

Thrombomodulin redirects thrombin from procoagulant to anticoagulant action. The complex activates protein C, which with protein S degrades factors Va and VIIIa and so limits clot extension beyond the injury site.

Option by option

A. Activates factor XIII to stabilise fibrin
Factor XIII activation is a procoagulant action of free thrombin.
B. Activates protein C, which inactivates factors Va and VIIIa (correct)
Correct. Activation of protein C turns thrombin into an anticoagulant.
C. Converts fibrinogen to fibrin at a faster rate
Free thrombin converts fibrinogen to fibrin; bound to thrombomodulin it loses this activity.
D. Activates platelets through protease-activated receptors
Platelet activation is a procoagulant action of free thrombin.

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.

Questions about this Physiology question

What is the answer to this Physiology question?

The best answer is B, Activates protein C, which inactivates factors Va and VIIIa. Thrombomodulin redirects thrombin from procoagulant to anticoagulant action.

Why is "Activates factor XIII to stabilise fibrin" not the answer?

Factor XIII activation is a procoagulant action of free thrombin.

Why is "Converts fibrinogen to fibrin at a faster rate" not the answer?

Free thrombin converts fibrinogen to fibrin; bound to thrombomodulin it loses this activity.

Why is "Activates platelets through protease-activated receptors" not the answer?

Platelet activation is a procoagulant action of free thrombin.

What concept does this question test?

It tests Blood and immunity: thrombomodulin in Physiology. The complex activates protein C, which with protein S degrades factors Va and VIIIa and so limits clot extension beyond the injury site.

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 Blood and immunity: thrombomodulin?

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.