Lipids: membrane phospholipids and signalling: 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 · Lipids: membrane phospholipids and signalling

Sample item

Activation of a Gq-coupled receptor stimulates phospholipase C, which hydrolyses a membrane phospholipid. Which pair of second messengers is generated?

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

The answer and the reasoning

D. Inositol trisphosphate and diacylglycerol

Phospholipase C cleaves phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate, which releases calcium from the endoplasmic reticulum, and diacylglycerol, which activates protein kinase C. This pathway mediates effects such as alpha-1 adrenergic vasoconstriction and muscarinic M3 signalling.

Option by option

  • A. Cyclic AMP and pyrophosphate

    Cyclic AMP and pyrophosphate are produced from ATP by adenylyl cyclase.

  • B. Phosphatidic acid and inositol

    Phosphatidic acid and inositol would not be the products of phospholipase C action on PIP2.

  • C. Ceramide and phosphocholine

    Ceramide and phosphocholine are the products of sphingomyelinase on sphingomyelin.

  • D. Inositol trisphosphate and diacylglycerol (correct)

    Correct. PIP2 splits into IP3 and diacylglycerol.

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 D, Inositol trisphosphate and diacylglycerol. Phospholipase C cleaves phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate, which releases calcium from the endoplasmic reticulum, and diacylglycerol, which activates protein kinase C.

Why is "Cyclic AMP and pyrophosphate" not the answer?

Cyclic AMP and pyrophosphate are produced from ATP by adenylyl cyclase.

Why is "Phosphatidic acid and inositol" not the answer?

Phosphatidic acid and inositol would not be the products of phospholipase C action on PIP2.

Why is "Ceramide and phosphocholine" not the answer?

Ceramide and phosphocholine are the products of sphingomyelinase on sphingomyelin.

What concept does this question test?

It tests Lipids: membrane phospholipids and signalling in Biochemistry. This pathway mediates effects such as alpha-1 adrenergic vasoconstriction and muscarinic M3 signalling.

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 Lipids: membrane phospholipids and signalling?

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.