Lipid metabolism: foam cell formation: 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: foam cell formation

Sample item

In early atherosclerosis, subendothelial macrophages become lipid-laden foam cells even though cellular cholesterol content is high. Which uptake pathway explains the continued cholesterol accumulation?

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

The answer and the reasoning

A. Scavenger receptor uptake of oxidised LDL, not down-regulated by cholesterol

Macrophages take up oxidatively modified LDL through scavenger receptors such as CD36. These receptors are not suppressed by rising intracellular cholesterol, unlike the LDL receptor, so cholesterol esters accumulate and produce foam cells in the fatty streak.

Option by option

  • A. Scavenger receptor uptake of oxidised LDL, not down-regulated by cholesterol (correct)

    Correct. Scavenger receptors take up oxidised LDL without feedback regulation, creating foam cells.

  • B. LDL receptor uptake, up-regulated by high cellular cholesterol

    The LDL receptor is down-regulated by high cellular cholesterol via SREBP, so it does not explain the accumulation.

  • C. Lipoprotein lipase hydrolysis of VLDL at the macrophage surface

    Lipoprotein lipase acts on triglyceride in chylomicrons and VLDL at capillary endothelium and is not the route of macrophage cholesterol loading.

  • D. Passive entry of HDL cholesterol through the membrane

    HDL removes cholesterol from cells through ABCA1 and ABCG1 and does not load macrophages.

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, Scavenger receptor uptake of oxidised LDL, not down-regulated by cholesterol. Macrophages take up oxidatively modified LDL through scavenger receptors such as CD36.

Why is "LDL receptor uptake, up-regulated by high cellular cholesterol" not the answer?

The LDL receptor is down-regulated by high cellular cholesterol via SREBP, so it does not explain the accumulation.

Why is "Lipoprotein lipase hydrolysis of VLDL at the macrophage surface" not the answer?

Lipoprotein lipase acts on triglyceride in chylomicrons and VLDL at capillary endothelium and is not the route of macrophage cholesterol loading.

Why is "Passive entry of HDL cholesterol through the membrane" not the answer?

HDL removes cholesterol from cells through ABCA1 and ABCG1 and does not load macrophages.

What concept does this question test?

It tests Lipid metabolism: foam cell formation in Biochemistry. These receptors are not suppressed by rising intracellular cholesterol, unlike the LDL receptor, so cholesterol esters accumulate and produce foam cells in the fatty streak.

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 Lipid metabolism: foam cell formation?

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.