Gastrointestinal physiology: short-chain fatty acids: 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 · Gastrointestinal physiology: short-chain fatty acids

Sample item

A patient with a defunctioned colon segment after ileostomy develops diversion colitis that improves with short-chain fatty acid enemas. Which short-chain fatty acid is the preferred energy source of colonocytes?

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

The answer and the reasoning

A. Butyrate

Colonic bacteria ferment undigested carbohydrate to short-chain fatty acids, and colonocytes obtain most of their energy from butyrate. Acetate passes to peripheral tissues and propionate is used by the liver for gluconeogenesis. A defunctioned segment is deprived of luminal butyrate.

Option by option

  • A. Butyrate (correct)

    Correct. Butyrate is the main colonocyte fuel.

  • B. Acetate

    Acetate is the most abundant but is mostly used by liver and muscle.

  • C. Propionate

    Propionate is mainly taken up by the liver for gluconeogenesis.

  • D. Lactate

    Lactate is not a major short-chain fatty acid product used by colonocytes.

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 A, Butyrate. Colonic bacteria ferment undigested carbohydrate to short-chain fatty acids, and colonocytes obtain most of their energy from butyrate.

Why is "Acetate" not the answer?

Acetate is the most abundant but is mostly used by liver and muscle.

Why is "Propionate" not the answer?

Propionate is mainly taken up by the liver for gluconeogenesis.

Why is "Lactate" not the answer?

Lactate is not a major short-chain fatty acid product used by colonocytes.

What concept does this question test?

It tests Gastrointestinal physiology: short-chain fatty acids in Physiology. Acetate passes to peripheral tissues and propionate is used by the liver for gluconeogenesis. A defunctioned segment is deprived of luminal butyrate.

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 Gastrointestinal physiology: short-chain fatty acids?

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.