Peroxisomal disorders: 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 · Peroxisomal disorders

Sample item

A hypotonic neonate has a high forehead, flat facies, hepatomegaly and seizures, with raised very long chain fatty acids in plasma. Which organelle function is deficient?

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

The answer and the reasoning

A. Peroxisome biogenesis

Zellweger spectrum disorders are caused by PEX gene mutations that impair peroxisome assembly. Very long chain fatty acids, phytanic acid and bile acid intermediates accumulate, and plasmalogen synthesis is impaired.

Option by option

  • A. Peroxisome biogenesis (correct)

    Correct. Peroxisomes are required for very long chain fatty acid oxidation.

  • B. Mitochondrial oxidative phosphorylation

    Respiratory chain defects raise lactate rather than VLCFA.

  • C. Lysosomal enzyme trafficking

    Defective lysosomal enzyme trafficking is I-cell disease, with coarse features and no VLCFA rise.

  • D. Golgi glycosylation of proteins

    Golgi glycosylation defects cause congenital disorders of glycosylation with abnormal transferrin.

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 A, Peroxisome biogenesis. Zellweger spectrum disorders are caused by PEX gene mutations that impair peroxisome assembly.

Why is "Mitochondrial oxidative phosphorylation" not the answer?

Respiratory chain defects raise lactate rather than VLCFA.

Why is "Lysosomal enzyme trafficking" not the answer?

Defective lysosomal enzyme trafficking is I-cell disease, with coarse features and no VLCFA rise.

Why is "Golgi glycosylation of proteins" not the answer?

Golgi glycosylation defects cause congenital disorders of glycosylation with abnormal transferrin.

What concept does this question test?

It tests Peroxisomal disorders in Biochemistry. Very long chain fatty acids, phytanic acid and bile acid intermediates accumulate, and plasmalogen synthesis is impaired.

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 Peroxisomal disorders?

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.