Enzymes: 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 · Enzymes

Sample item

What happens to both Km and Vmax in noncompetitive inhibition?

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

The answer and the reasoning

D. Vmax decreases with unchanged Km

Pure noncompetitive inhibition reduces the number of effectively functioning enzyme molecules, lowering Vmax while substrate affinity represented by Km remains unchanged.

Option by option

  • A. Both become zero

    Enzyme activity is reduced, not necessarily completely absent.

  • B. Both always increase

    Both parameters do not necessarily increase together.

  • C. Km increases with unchanged Vmax

    This pattern describes competitive inhibition instead.

  • D. Vmax decreases with unchanged Km (correct)

    Correct: pure noncompetitive inhibition lowers Vmax without changing Km.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, Vmax decreases with unchanged Km. Pure noncompetitive inhibition reduces the number of effectively functioning enzyme molecules, lowering Vmax while substrate affinity represented by Km remains unchanged.

Why is "Both become zero" not the answer?

Enzyme activity is reduced, not necessarily completely absent.

Why is "Both always increase" not the answer?

Both parameters do not necessarily increase together.

Why is "Km increases with unchanged Vmax" not the answer?

This pattern describes competitive inhibition instead.

What concept does this question test?

It tests Enzymes in Biochemistry. The correct option holds because: Correct: pure noncompetitive inhibition lowers Vmax without changing Km.

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 Enzymes?

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.