Phospholipids: cardiolipin and Barth syndrome: 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 · Phospholipids: cardiolipin and Barth syndrome

Sample item

An infant boy has dilated cardiomyopathy, cyclical neutropenia and skeletal myopathy, with 3-methylglutaconic aciduria. The disorder is caused by tafazzin mutation affecting remodelling of which phospholipid?

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

The answer and the reasoning

B. Cardiolipin

Tafazzin is a transacylase that remodels cardiolipin, a phospholipid found almost exclusively in the inner mitochondrial membrane, where it stabilises respiratory complexes. Defective cardiolipin in Barth syndrome impairs oxidative phosphorylation in heart, muscle and neutrophils. It is X-linked recessive.

Option by option

  • A. Phosphatidylinositol 4,5-bisphosphate

    Phosphatidylinositol bisphosphate is the substrate of phospholipase C in signalling and is unrelated to this syndrome.

  • B. Cardiolipin (correct)

    Abnormal cardiolipin in the inner mitochondrial membrane impairs energy production in high-demand tissues.

  • C. Sphingomyelin

    Sphingomyelin disorders such as Niemann-Pick disease affect lysosomal storage and not mitochondrial function.

  • D. Phosphatidylcholine

    Dipalmitoyl phosphatidylcholine is the major component of lung surfactant and is not remodelled by tafazzin.

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 Biochemistry question

What is the answer to this Biochemistry question?

The best answer is B, Cardiolipin. Tafazzin is a transacylase that remodels cardiolipin, a phospholipid found almost exclusively in the inner mitochondrial membrane, where it stabilises respiratory complexes.

Why is "Phosphatidylinositol 4,5-bisphosphate" not the answer?

Phosphatidylinositol bisphosphate is the substrate of phospholipase C in signalling and is unrelated to this syndrome.

Why is "Sphingomyelin" not the answer?

Sphingomyelin disorders such as Niemann-Pick disease affect lysosomal storage and not mitochondrial function.

Why is "Phosphatidylcholine" not the answer?

Dipalmitoyl phosphatidylcholine is the major component of lung surfactant and is not remodelled by tafazzin.

What concept does this question test?

It tests Phospholipids: cardiolipin and Barth syndrome in Biochemistry. Defective cardiolipin in Barth syndrome impairs oxidative phosphorylation in heart, muscle and neutrophils. It is X-linked recessive.

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 Phospholipids: cardiolipin and Barth syndrome?

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.