Nutrition: protein quality: 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: protein quality

Sample item

In a balance study a subject ingests 10 g of nitrogen, loses 2 g in faeces and 3 g in urine, ignoring endogenous losses. What are the biological value (BV) and net protein utilisation (NPU) of the dietary protein?

ABV 80% and NPU 50%BBV 62.5% and NPU 50%CBV 62.5% and NPU 80%DBV 50% and NPU 62.5%

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

The answer and the reasoning

B. BV 62.5% and NPU 50%

Nitrogen retained is 10 - 2 - 3 = 5 g. BV is retained nitrogen divided by absorbed nitrogen, 5 / 8 = 62.5%, while NPU is retained nitrogen divided by intake, 5 / 10 = 50%. The ratio 8 / 10 = 80% is digestibility, so NPU equals BV multiplied by digestibility.

Option by option

A. BV 80% and NPU 50%
Eighty percent is digestibility and not BV.
B. BV 62.5% and NPU 50% (correct)
Correct. BV uses absorbed nitrogen and NPU uses intake nitrogen.
C. BV 62.5% and NPU 80%
NPU cannot exceed BV, and 80% is the digestibility.
D. BV 50% and NPU 62.5%
The two figures are swapped; NPU is always lower than or equal to BV.

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 B, BV 62.5% and NPU 50%. Nitrogen retained is 10 - 2 - 3 = 5 g.

Why is "BV 80% and NPU 50%" not the answer?

Eighty percent is digestibility and not BV.

Why is "BV 62.5% and NPU 80%" not the answer?

NPU cannot exceed BV, and 80% is the digestibility.

Why is "BV 50% and NPU 62.5%" not the answer?

The two figures are swapped; NPU is always lower than or equal to BV.

What concept does this question test?

It tests Nutrition: protein quality in Biochemistry. BV is retained nitrogen divided by absorbed nitrogen, 5 / 8 = 62.5%, while NPU is retained nitrogen divided by intake, 5 / 10 = 50%. The ratio 8 / 10 = 80% is digestibility, so NPU equals BV multiplied by digestibility.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: protein quality?

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.