Cholesterol is found within the phospholipid bilayer of the cell (plasma) membrane, tucked between the phospholipid molecules with part of it near the heads and the rest down among the tails.

Exact location

  • Cholesterol is mainly located in the plasma (cell) membrane, where it can make up a large fraction of the membrane lipids.
  • It inserts itself between the phospholipids of the bilayer, not as a separate layer on top or bottom.

How it is oriented

  • The small hydroxyl (–OH) group of cholesterol lies close to the hydrophilic phospholipid heads at the membrane surface.
  • The bulky steroid rings and hydrocarbon tail extend into the hydrophobic core alongside the fatty acid tails of phospholipids.

Which side of the bilayer

  • Cholesterol is present in both leaflets of the bilayer, though in many mammalian cells it is somewhat enriched in the outer leaflet and in cholesterol-rich “lipid rafts.”
  • These cholesterol- and sphingolipid-rich rafts form more ordered microdomains within the membrane where many signaling proteins cluster.