Plasma proteins: albumin as a carrier: 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 · Plasma proteins: albumin as a carrier

Sample item

A jaundiced preterm neonate is given a sulfonamide for infection and develops kernicterus at a bilirubin level lower than expected. Which mechanism best explains this?

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

The answer and the reasoning

C. The drug displaces unconjugated bilirubin from albumin, raising free bilirubin that crosses the blood-brain barrier

Albumin carries unconjugated bilirubin in plasma, and only the unbound fraction can enter the brain. Sulfonamides and ceftriaxone compete for albumin binding sites, so free bilirubin rises even when total bilirubin is modest. In preterm neonates, low albumin and an immature blood-brain barrier increase the risk of kernicterus.

Option by option

  • A. The drug increases intestinal absorption of conjugated bilirubin

    Conjugated bilirubin absorption does not cause kernicterus; the toxic form is unconjugated bilirubin.

  • B. The drug lowers hepatic albumin synthesis

    The effect is acute displacement and not a change in albumin production.

  • C. The drug displaces unconjugated bilirubin from albumin, raising free bilirubin that crosses the blood-brain barrier (correct)

    Correct. Competitive displacement from albumin increases free, neurotoxic bilirubin.

  • D. The drug irreversibly inhibits bilirubin glucuronidation

    The danger comes from displacement, not from irreversible blocking of UDP-glucuronosyltransferase.

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.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, The drug displaces unconjugated bilirubin from albumin, raising free bilirubin that crosses the blood-brain barrier. Albumin carries unconjugated bilirubin in plasma, and only the unbound fraction can enter the brain.

Why is "The drug increases intestinal absorption of conjugated bilirubin" not the answer?

Conjugated bilirubin absorption does not cause kernicterus; the toxic form is unconjugated bilirubin.

Why is "The drug lowers hepatic albumin synthesis" not the answer?

The effect is acute displacement and not a change in albumin production.

Why is "The drug irreversibly inhibits bilirubin glucuronidation" not the answer?

The danger comes from displacement, not from irreversible blocking of UDP-glucuronosyltransferase.

What concept does this question test?

It tests Plasma proteins: albumin as a carrier in Biochemistry. Sulfonamides and ceftriaxone compete for albumin binding sites, so free bilirubin rises even when total bilirubin is modest. In preterm neonates, low albumin and an immature blood-brain barrier increase the risk of kernicterus.

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 Plasma proteins: albumin as a carrier?

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.