Figure 1.

A phosphatidylinositol structure. This figure is originated from http://en.wikipedia.org/wiki/File:Phosphatidylinositol.jpg. The hydroxyl moieties at 3', 4', and 5' in the head group can be phosphorylated to produce seven phosphoinositides, phosphatidylinositol 3-phosphate (PI3P), phosphatidylinositol 4-phosphate (PI4P), phosphatidylinositol 5-phosphate (PI5P), phosphatidylinositol (3,4)-bisphosphate (PI(3,4)P₂), phosphatidylinositol (3,5)-bisphosphate (PI(3,5)P₂), phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P₂), and phosphatidylinositol (3,4,5)-trisphosphate (PI(3,4,5)P₃, PIP₃).