Amino acid metabolism: PAPS as sulfate donor: 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.

Try it

Biochemistry · Amino acid metabolism: PAPS as sulfate donor

Sample item

The sulfation of glycosaminoglycans, steroids and xenobiotics uses an activated form of sulfate. What is this universal sulfate donor?

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

The answer and the reasoning

D. 3'-Phosphoadenosine 5'-phosphosulfate (PAPS)

PAPS is made from ATP and inorganic sulfate in two steps and donates sulfate in sulfotransferase reactions, as in chondroitin and heparan sulfate synthesis and phase II drug conjugation. Sulfate is produced from the sulfur of cysteine. S-adenosylmethionine donates methyl groups, and UDP-glucuronic acid donates glucuronate.

Option by option

  • A. Acetyl-CoA

    Acetyl-CoA donates acetyl groups for acetylation.

  • B. S-adenosylmethionine

    S-adenosylmethionine donates methyl groups, not sulfate.

  • C. UDP-glucuronic acid

    UDP-glucuronic acid donates glucuronate for conjugation, not sulfate.

  • D. 3'-Phosphoadenosine 5'-phosphosulfate (PAPS) (correct)

    Correct. PAPS is the activated sulfate donor for sulfotransferases.

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, 3'-Phosphoadenosine 5'-phosphosulfate (PAPS). PAPS is made from ATP and inorganic sulfate in two steps and donates sulfate in sulfotransferase reactions, as in chondroitin and heparan sulfate synthesis and phase II drug conjugation.

Why is "Acetyl-CoA" not the answer?

Acetyl-CoA donates acetyl groups for acetylation.

Why is "S-adenosylmethionine" not the answer?

S-adenosylmethionine donates methyl groups, not sulfate.

Why is "UDP-glucuronic acid" not the answer?

UDP-glucuronic acid donates glucuronate for conjugation, not sulfate.

What concept does this question test?

It tests Amino acid metabolism: PAPS as sulfate donor in Biochemistry. Sulfate is produced from the sulfur of cysteine. S-adenosylmethionine donates methyl groups, and UDP-glucuronic acid donates glucuronate.

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 Amino acid metabolism: PAPS as sulfate donor?

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.