Lipid metabolism: cholesterol gallstones: 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 · Lipid metabolism: cholesterol gallstones

Sample item

A 42-year-old obese woman has cholesterol gallstones. Which abnormality of bile composition favours cholesterol crystal formation?

AExcess bile salts relative to cholesterolBExcess conjugated bilirubin without cholesterol changeCExcess cholesterol relative to bile salts and phospholipidDExcess phospholipid relative to cholesterol

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

The answer and the reasoning

C. Excess cholesterol relative to bile salts and phospholipid

Cholesterol is insoluble and is kept in mixed micelles and vesicles by bile salts and lecithin. Supersaturation arises when cholesterol secretion rises, as in obesity, or when bile salt and phospholipid secretion falls. Crystal nucleation then leads to stones.

Option by option

A. Excess bile salts relative to cholesterol
A relative excess of bile salts keeps cholesterol solubilised and protects against stone formation.
B. Excess conjugated bilirubin without cholesterol change
Conjugated bilirubin excess is not the cause of cholesterol stones; pigment stones relate to unconjugated bilirubin.
C. Excess cholesterol relative to bile salts and phospholipid (correct)
Correct. Cholesterol supersaturation relative to bile salts and lecithin leads to crystals and stones.
D. Excess phospholipid relative to cholesterol
More phospholipid also keeps cholesterol soluble, so it does not promote stones.

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.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, Excess cholesterol relative to bile salts and phospholipid. Cholesterol is insoluble and is kept in mixed micelles and vesicles by bile salts and lecithin.

Why is "Excess bile salts relative to cholesterol" not the answer?

A relative excess of bile salts keeps cholesterol solubilised and protects against stone formation.

Why is "Excess conjugated bilirubin without cholesterol change" not the answer?

Conjugated bilirubin excess is not the cause of cholesterol stones; pigment stones relate to unconjugated bilirubin.

Why is "Excess phospholipid relative to cholesterol" not the answer?

More phospholipid also keeps cholesterol soluble, so it does not promote stones.

What concept does this question test?

It tests Lipid metabolism: cholesterol gallstones in Biochemistry. Supersaturation arises when cholesterol secretion rises, as in obesity, or when bile salt and phospholipid secretion falls. Crystal nucleation then leads to stones.

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 Lipid metabolism: cholesterol gallstones?

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.