Phospholipid
A lipid in which one fatty acid of a triglyceride is replaced by a phosphate-containing group.
Unit
Dimensionless
In depth
The result is an amphipathic molecule with a hydrophilic head and two hydrophobic tails. In water such molecules spontaneously assemble into a bilayer with tails inward, which is the fundamental architecture of every biological membrane.
Examples in the real world
Lecithin in egg yolk, used as an emulsifier; the phospholipid bilayer enclosing every living cell.