General physiology: peroxisomal function: 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 · General physiology: peroxisomal function

Sample item

A hypotonic neonate has a high forehead, hepatomegaly and seizures. Plasma shows accumulation of unusual long fatty acids, and liver electron microscopy shows absence of the catalase-containing organelle. Which function is lost?

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

The answer and the reasoning

C. Chain-shortening of very long-chain fatty acids

Peroxisomes contain catalase and the enzymes that begin beta-oxidation of very long-chain fatty acids, and they take part in plasmalogen synthesis. When peroxisomes fail to form, as in Zellweger syndrome, these fatty acids accumulate and cause neurological and hepatic disease.

Option by option

  • A. Glycosylation and sorting of secretory proteins

    Glycosylation and sorting of secretory proteins occur in the endoplasmic reticulum and Golgi.

  • B. Oxidation of short-chain fatty acids for ATP

    Short-chain fatty acid oxidation occurs in mitochondria, which are present in this child.

  • C. Chain-shortening of very long-chain fatty acids (correct)

    Correct. Peroxisomes shorten very long-chain fatty acids before they enter mitochondria.

  • D. Hydrolysis of glycolipids at acid pH

    Acid hydrolysis of glycolipids is a lysosomal function.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Chain-shortening of very long-chain fatty acids. Peroxisomes contain catalase and the enzymes that begin beta-oxidation of very long-chain fatty acids, and they take part in plasmalogen synthesis.

Why is "Glycosylation and sorting of secretory proteins" not the answer?

Glycosylation and sorting of secretory proteins occur in the endoplasmic reticulum and Golgi.

Why is "Oxidation of short-chain fatty acids for ATP" not the answer?

Short-chain fatty acid oxidation occurs in mitochondria, which are present in this child.

Why is "Hydrolysis of glycolipids at acid pH" not the answer?

Acid hydrolysis of glycolipids is a lysosomal function.

What concept does this question test?

It tests General physiology: peroxisomal function in Physiology. When peroxisomes fail to form, as in Zellweger syndrome, these fatty acids accumulate and cause neurological and hepatic disease.

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 General physiology: peroxisomal function?

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.