Final answer:
Phospholipids are the main components of cell membranes, except phosphatidylcholine and phosphatidylserine, which are found in plasma membranes.
Step-by-step explanation:
Phospholipids are a type of lipid that contain a phosphate group and are the primary component of cell membranes. They consist of a hydrophilic head and a hydrophobic tail. Phospholipids are important components of the plasma membrane of cells. They also include phosphatidylcholine and phosphatidylserine, which are found in plasma membranes.