Biomolecules: glycosaminoglycans: 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: glycosaminoglycans

Sample item

Analysis of a viscous fluid aspirated from a knee joint shows a glycosaminoglycan made of repeating glucuronic acid and N-acetylglucosamine units. It carries no sulfate groups and is not attached to a core protein. Which glycosaminoglycan is this?

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

The answer and the reasoning

A. Hyaluronic acid

Hyaluronic acid is the only major glycosaminoglycan that is unsulfated and free of a protein core. Its long hydrated chains give synovial fluid and vitreous humour their viscosity and lubricating properties. The other three are sulfated and occur covalently attached to core proteins as proteoglycans.

Option by option

  • A. Hyaluronic acid (correct)

    Correct. It is unsulfated, protein-free and builds the viscosity of synovial fluid.

  • B. Heparin

    Heparin is the most highly sulfated glycosaminoglycan in the body, so it cannot be unsulfated.

  • C. Chondroitin sulfate

    Chondroitin sulfate is sulfated and bound to aggrecan core protein in cartilage.

  • D. Keratan sulfate

    Keratan sulfate is sulfated and found mainly in cornea and cartilage proteoglycans.

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 A, Hyaluronic acid. Hyaluronic acid is the only major glycosaminoglycan that is unsulfated and free of a protein core.

Why is "Heparin" not the answer?

Heparin is the most highly sulfated glycosaminoglycan in the body, so it cannot be unsulfated.

Why is "Chondroitin sulfate" not the answer?

Chondroitin sulfate is sulfated and bound to aggrecan core protein in cartilage.

Why is "Keratan sulfate" not the answer?

Keratan sulfate is sulfated and found mainly in cornea and cartilage proteoglycans.

What concept does this question test?

It tests Biomolecules: glycosaminoglycans in Biochemistry. Its long hydrated chains give synovial fluid and vitreous humour their viscosity and lubricating properties. The other three are sulfated and occur covalently attached to core proteins as proteoglycans.

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 Biomolecules: glycosaminoglycans?

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.