Which step in the reverse cholesterol transport pathway requires lecithin:cholesterol acyltransferase (LCAT) activity?

• A Transfer of CE from HDL to VLDL via CETP
• B Uptake of CE-rich HDL by hepatic SR-BI receptor
• C Conversion of cholesteryl ester to bile acids in liver
• D Esterification of free cholesterol on nascent HDL to cholesteryl ester (CE), trapping cholesterol in the HDL core ✓

Explanation

Nascent HDL (discoidal) acquires free cholesterol from peripheral cell membranes via ABCA1. LCAT (activated by apoA-I) esterifies free cholesterol using a fatty acid from phosphatidylcholine, forming cholesteryl ester (CE). CE is hydrophobic and migrates to the HDL core, converting discoidal HDL to spherical HDL3 and then HDL2. This esterification step is essential for maintaining the free cholesterol gradient that drives continued efflux from cells. LCAT deficiency results in corneal opacities and low HDL.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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