Phospholipids show similarities with the triglycerides: the glycerol molecule is again esterified three times. Two of the alcohol groups are esterified by a fatty acid, but the third forms a phosphate ester with phosphoric acid.

This phosphoric acid is esterified a second time with lower alcohols such as 2-amino-ethanol (1), serine (2), choline (3) and inositol (4).
Here, too, the structure of the molecule gives rise to a polar head (blue) and an apolar tail (yellow).