Biomolecules and enzymes: Anfinsen experiment: 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 · Biomolecules and enzymes: Anfinsen experiment

Sample item

Ribonuclease treated with urea and beta-mercaptoethanol loses all activity. When both agents are removed slowly, activity returns and the correct disulfide bonds re-form. What principle does this demonstrate?

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

The answer and the reasoning

B. The primary sequence contains the information for native folding

Anfinsen showed that a denatured protein can refold spontaneously into its native conformation because the amino acid sequence specifies the structure. Urea disrupts non-covalent forces and mercaptoethanol reduces disulfides, but neither breaks peptide bonds.

Option by option

  • A. Disulfide bonds alone determine tertiary structure

    Disulfide bonds stabilise the fold but form correctly only because the sequence directs the folding.

  • B. The primary sequence contains the information for native folding (correct)

    Correct. Spontaneous refolding shows that the amino acid sequence determines the native structure.

  • C. Peptide bonds are broken and re-formed during renaturation

    Urea and a reducing agent leave peptide bonds intact, so none are re-formed on renaturation.

  • D. Folding always requires an ATP-dependent chaperone

    Refolding occurred in a test tube without chaperones or ATP, so these are not essential in this example.

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 B, The primary sequence contains the information for native folding. Anfinsen showed that a denatured protein can refold spontaneously into its native conformation because the amino acid sequence specifies the structure.

Why is "Disulfide bonds alone determine tertiary structure" not the answer?

Disulfide bonds stabilise the fold but form correctly only because the sequence directs the folding.

Why is "Peptide bonds are broken and re-formed during renaturation" not the answer?

Urea and a reducing agent leave peptide bonds intact, so none are re-formed on renaturation.

Why is "Folding always requires an ATP-dependent chaperone" not the answer?

Refolding occurred in a test tube without chaperones or ATP, so these are not essential in this example.

What concept does this question test?

It tests Biomolecules and enzymes: Anfinsen experiment in Biochemistry. Urea disrupts non-covalent forces and mercaptoethanol reduces disulfides, but neither breaks peptide bonds.

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 Biomolecules and enzymes: Anfinsen experiment?

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.