The phosphate group contribute the following functional features to the structure of phospholipids:
1. Negative charge to interact with water.
2. Place to attach another small molecule.
The phosphate group is made up of four atoms of oxygen which are attached to one atom of phosphorus. This molecule has a net negative charge of -3. In the phospholipid molecule, the phosphate enhanced the polarity of the phospholipid head by mean of its negative charge which react with water. Phosphate group also provide a point where other small molecules such as alcohol, serine, etc can be attached.