Phospholipids are an important class of lipids that serve multiple functions in cell membranes. Some common synonym for phospholipids includes phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and sphingomyelin. These lipids consist of a hydrophilic head group and a hydrophobic tail. Phosphatidylcholine is the most abundant phospholipid in membranes and is involved in signaling and cell adhesion. Phosphatidylethanolamine is essential for membrane integrity, and phosphatidylserine is important for cell signaling and apoptosis. Phosphatidylinositol plays a key role in signaling pathways, while sphingomyelin is primarily found in the plasma membrane of animal cells.