Lipoproteins vary significantly in size, with chylomicrons being the largest and HDL the smallest among the given options. The correct increasing order of diameter is HDL, LDL, VLDL, and chylomicron.

Correct Answer

Option 1: A, D, B, C (HDL < LDL < VLDL < Chylomicron)
This sequence reflects the standard sizes: HDL (~5-12 nm), LDL (~18-25 nm), VLDL (~30-80 nm), and chylomicrons (75-1200 nm ex vivo, averaging largest).

HDL (A) Details

High-density lipoprotein (HDL) particles are the smallest, typically ranging from 5-12 nm in diameter. They are protein-rich (apoA-I dominant) and carry cholesterol from tissues to the liver, earning the “good cholesterol” label. Small size aids rapid reverse transport but limits lipid payload.

LDL (D) Details

Low-density lipoprotein (D) measures about 18-25 nm, larger than HDL due to higher cholesterol ester content and apoB-100. Known as “bad cholesterol,” it delivers cholesterol to cells but excess contributes to atherosclerosis. Size allows moderate lipid transport compared to denser HDL.​

VLDL (B) Details

Very low-density lipoprotein (B) spans 30-80 nm, bigger than LDL as it packages triglycerides from the liver for peripheral delivery. Triglyceride-rich core with apoB-100; it shrinks to IDL/LDL after lipolysis. Larger than LDL, it precedes remnants in density gradient.​

Chylomicron (C) Details

Chylomicrons (C) are the largest at 75-1200 nm, formed in intestines to absorb dietary lipids (triglycerides dominant, apoB-48). Least dense due to massive lipid droplet; they shrink post-lipolysis but start biggest among options. Essential for fat absorption, not liver-synthesized.

Why This Order?

Diameter inversely correlates with density: larger lipid cores mean lower density (chylomicron < VLDL < LDL < HDL). NMR and ultracentrifugation confirm HDL smallest (~7-14 nm range), chylomicrons largest. Other options fail: e.g., option 4 skips LDL properly.