Nutrition: respiratory quotient: 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 · Nutrition: respiratory quotient

Sample item

In a metabolic study, a fasting subject consumes 300 mL of oxygen per minute and produces 210 mL of carbon dioxide per minute. Which fuel is being oxidised predominantly?

AFatBCarbohydrate converted into fat (net lipogenesis)CProteinDCarbohydrate

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

The answer and the reasoning

A. Fat

The respiratory quotient is carbon dioxide produced divided by oxygen consumed, which is 210 divided by 300, or 0.7. This value is characteristic of fat oxidation. Carbohydrate gives 1.0, protein about 0.8 and net lipogenesis can push the value above 1.0.

Option by option

A. Fat (correct)
Correct. A quotient of 0.7 indicates mainly fat oxidation.
B. Carbohydrate converted into fat (net lipogenesis)
Net lipogenesis gives a quotient above 1.0, because carbon dioxide is formed without matching oxygen use.
C. Protein
Protein oxidation gives a quotient of about 0.8.
D. Carbohydrate
Pure carbohydrate oxidation gives a quotient of 1.0.

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.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Fat. The respiratory quotient is carbon dioxide produced divided by oxygen consumed, which is 210 divided by 300, or 0.

Why is "Carbohydrate converted into fat (net lipogenesis)" not the answer?

Net lipogenesis gives a quotient above 1.0, because carbon dioxide is formed without matching oxygen use.

Why is "Protein" not the answer?

Protein oxidation gives a quotient of about 0.8.

Why is "Carbohydrate" not the answer?

Pure carbohydrate oxidation gives a quotient of 1.0.

What concept does this question test?

It tests Nutrition: respiratory quotient in Biochemistry. 7. This value is characteristic of fat oxidation. Carbohydrate gives 1.0, protein about 0.8 and net lipogenesis can push the value above 1.0.

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 Nutrition: respiratory quotient?

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.