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Nutrition · Chapter 4

Cholesterol Traffic

Cholesterol will not dissolve in blood, so it travels inside protein-wrapped particles called lipoproteins. The famous two — LDL and HDL — carry the very same cholesterol molecule, but they run in opposite directions: one delivering it out to the tissues, one collecting it back for disposal. Follow the traffic, build a particle, then watch a lipid panel split cholesterol by direction of travel.

The traffic map

outbound (apoB particles)inbound (HDL)protein shell
There is no second kind of cholesterol Cholesterol is one molecule, C27H46O. It is not made in two flavours. LDL and HDL are not kinds of cholesterol at all — they are delivery vehicles, and their names come from how they float when spun in an ultracentrifuge: low- and high-density lipoprotein. A lipid panel does not measure the particles; it measures the cholesterol riding inside them, which is why the results are written LDL-C and HDL-C. The everyday habit of calling one "good" and the other "bad" hides the actual lesson: same cargo, opposite direction.
Cholesterol trafficfive carriers, two directions
Direction—
Core cargo—
Address label—