Lipid Biochemistry USMLE Step 1 Practice Question
A 52-year-old woman with primary biliary cirrhosis presents with xanthomas and jaundice. Vital signs: BP 128/82, HR 88, RR 16, Temp 37°C, SpO2 98%. Labs show alkaline phosphatase 320 U/L, total cholesterol 580 mg/dL, and large LDL particles on lipoprotein electrophoresis. She denies chest pain or dyspnea. Despite severe hypercholesterolemia, coronary angiography shows no atherosclerotic lesions. Which structural feature of her abnormally large LDL particles best explains this delayed atherogenicity?
Answer choices
- AEnhanced expression of macrophage scavenger receptors
- BReduced synthesis of cholesteryl ester transfer protein
- CIncreased hepatic uptake via LDL receptors
- DIncreased oxidation of apolipoprotein B-100
- ELarge particle size limits arterial wall penetrationCorrect answer
- FDeficient apolipoprotein C-II content reducing triglyceride hydrolysis
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