Biomolecules and enzymes: lysosomal storage: 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 · Biomolecules and enzymes: lysosomal storage

Sample item

A 3-year-old boy has coarse facies, hepatosplenomegaly, joint stiffness and aggressive behaviour. His corneas are clear and a maternal uncle had the same illness. Which enzyme is deficient?

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

The answer and the reasoning

D. Iduronate-2-sulfatase

Hunter syndrome is X-linked recessive and due to iduronate-2-sulfatase deficiency, with dermatan and heparan sulfate accumulating. Clear corneas separate it from Hurler syndrome. Boys are affected.

Option by option

  • A. Alpha-L-iduronidase

    Alpha-L-iduronidase deficiency is Hurler syndrome, autosomal recessive with corneal clouding.

  • B. Heparan N-sulfatase

    Heparan N-sulfatase deficiency is Sanfilippo A with severe neurological decline and little coarseness.

  • C. Galactose-6-sulfatase

    Galactose-6-sulfatase deficiency is Morquio A, with skeletal dysplasia and normal intelligence.

  • D. Iduronate-2-sulfatase (correct)

    Correct. X-linked inheritance with clear corneas fits Hunter syndrome.

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, Iduronate-2-sulfatase. Hunter syndrome is X-linked recessive and due to iduronate-2-sulfatase deficiency, with dermatan and heparan sulfate accumulating.

Why is "Alpha-L-iduronidase" not the answer?

Alpha-L-iduronidase deficiency is Hurler syndrome, autosomal recessive with corneal clouding.

Why is "Heparan N-sulfatase" not the answer?

Heparan N-sulfatase deficiency is Sanfilippo A with severe neurological decline and little coarseness.

Why is "Galactose-6-sulfatase" not the answer?

Galactose-6-sulfatase deficiency is Morquio A, with skeletal dysplasia and normal intelligence.

What concept does this question test?

It tests Biomolecules and enzymes: lysosomal storage in Biochemistry. Clear corneas separate it from Hurler syndrome. Boys are affected.

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: lysosomal storage?

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.