The phospholipids or phosphatides are a heterogeneous group of compounds that have the ester phosphorus. Phospholipids are the main lipid constituents of membranes, myelin sheath, microsomes and mitochondria.

Phosphatidic acid  is important as an intermediate in the synthesis of triacyglycerols as well as  phosphoglycerols. Phosphoglycerides have two different kinds of groups, a polar, hydrophilic group and hydrophobic, nonpolar tails. They are therefore amphipathic.

Saturated C16 or C18  fatty acids occur at the C1 position of the glyceropholipids, and the C2 position is often occupied by an unsaturated C16 to C22 fatty acid. Individual phospholipids are named according to the identities of these fatty acid residues. 

Phospholipids are classified according to the subconstituent X on the phosphate group. If X is a hydrogen, the compound is called 3sn phosphatidic acid. If X- OH is choline, it is called phosphatidyl choline (lecithin). The other major phospholipids are listed below.

Ethanolamine- Phosphatidyl ethanolamine.

Serine-  Phosphatidyl Serine

Glycerol-Phosphatidyl Glycerol

Phosphatidyl glycerol-Diphosphatidyl glycerol

Myo-inositol-Phosphatidylinositol.