Phospholipids serve as a permeable barrier for the cell membrane and its internal organelles. They also provide support and serve as the site for catalytic processes. They have roles in signal transduction and are precursors for signaling processes and the synthesis of molecules.
Phospholipids are molecules containing a glycerol bound to two fatty acids and a phosphate group. They contain both hydrophillic (water-loving) and hydrophobic (water-fearing) parts. These are the hydrophillic head and the hydrophobic tail, respectively. Phospholipids are the major component of biological membranes of organisms. It is there where they form what is known as the lipid bilayer.