Bioenergetics: brown adipose tissue: 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 · Bioenergetics: brown adipose tissue

Sample item

Newborns maintain body temperature partly by non-shivering thermogenesis in brown adipose tissue. Which mechanism produces heat in these cells?

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

The answer and the reasoning

B. Thermogenin (UCP1) lets protons re-enter the matrix, bypassing ATP synthase

In brown fat, noradrenaline stimulates lipolysis, and the released fatty acids activate uncoupling protein 1. This protein forms a proton channel in the inner mitochondrial membrane, so the gradient dissipates as heat instead of driving ATP synthesis. Oxidation therefore continues at a high rate without ATP being made.

Option by option

  • A. Increased ATP-ADP translocase exchange, which accelerates ATP synthesis

    Faster ATP-ADP exchange would support ATP production, not heat generation.

  • B. Thermogenin (UCP1) lets protons re-enter the matrix, bypassing ATP synthase (correct)

    UCP1 dissipates the proton gradient, giving heat in place of ATP.

  • C. Inhibition of ATP synthase, as caused by oligomycin

    Oligomycin blocks the proton channel of ATP synthase and halts respiration, which does not generate heat.

  • D. Blockade of cytochrome c oxidase, as caused by cyanide

    Cyanide stops electron flow at complex IV, and the cell is poisoned rather than heated.

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, Thermogenin (UCP1) lets protons re-enter the matrix, bypassing ATP synthase. In brown fat, noradrenaline stimulates lipolysis, and the released fatty acids activate uncoupling protein 1.

Why is "Increased ATP-ADP translocase exchange, which accelerates ATP synthes…" not the answer?

Faster ATP-ADP exchange would support ATP production, not heat generation.

Why is "Inhibition of ATP synthase, as caused by oligomycin" not the answer?

Oligomycin blocks the proton channel of ATP synthase and halts respiration, which does not generate heat.

Why is "Blockade of cytochrome c oxidase, as caused by cyanide" not the answer?

Cyanide stops electron flow at complex IV, and the cell is poisoned rather than heated.

What concept does this question test?

It tests Bioenergetics: brown adipose tissue in Biochemistry. This protein forms a proton channel in the inner mitochondrial membrane, so the gradient dissipates as heat instead of driving ATP synthesis. Oxidation therefore continues at a high rate without ATP being made.

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 Bioenergetics: brown adipose tissue?

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.