Lipid metabolism: platelet-activating factor: practice question

A Biochemistry 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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Biochemistry · Lipid metabolism: platelet-activating factor

Sample item

A mediator released by activated neutrophils and macrophages is an ether-linked phospholipid with an alkyl chain at position 1 and an acetyl group at position 2 of glycerol. It causes platelet aggregation, bronchoconstriction and increased vascular permeability. What is it?

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

The answer and the reasoning

B. Platelet-activating factor

Platelet-activating factor is 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine. It is formed from an ether phospholipid after phospholipase A2 action and acetylation, and it acts through a G-protein-coupled receptor in allergy and inflammation.

Option by option

  • A. Prostacyclin

    Prostacyclin is a cyclo-oxygenase product that inhibits platelet aggregation and is not a phospholipid.

  • B. Platelet-activating factor (correct)

    Correct. This ether-linked acetylated phosphatidylcholine is platelet-activating factor.

  • C. Leukotriene B4

    Leukotriene B4 is a lipoxygenase product that attracts neutrophils, and it is not a phospholipid.

  • D. Lysolecithin

    Lysolecithin is a membrane-disrupting phospholipid made by lecithinase and has no acetyl group at position 2.

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 Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Platelet-activating factor. Platelet-activating factor is 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine.

Why is "Prostacyclin" not the answer?

Prostacyclin is a cyclo-oxygenase product that inhibits platelet aggregation and is not a phospholipid.

Why is "Leukotriene B4" not the answer?

Leukotriene B4 is a lipoxygenase product that attracts neutrophils, and it is not a phospholipid.

Why is "Lysolecithin" not the answer?

Lysolecithin is a membrane-disrupting phospholipid made by lecithinase and has no acetyl group at position 2.

What concept does this question test?

It tests Lipid metabolism: platelet-activating factor in Biochemistry. It is formed from an ether phospholipid after phospholipase A2 action and acetylation, and it acts through a G-protein-coupled receptor in allergy and inflammation.

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 Lipid metabolism: platelet-activating factor?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry 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.