Final answer:
The cell membrane is primarily composed of a phospholipid bilayer, with proteins and carbohydrate chains playing important roles as well.
Step-by-step explanation:
The cell membrane is composed primarily of a phospholipid bilayer, which consists of two layers of phospholipid molecules. Phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. This arrangement allows the cell membrane to form a barrier between the cell and its surroundings. In addition to phospholipids, the cell membrane also contains proteins that are embedded within the phospholipid bilayer. These proteins have various functions, such as transporting molecules across the membrane and facilitating cell-cell communication. Finally, the cell membrane may also contain carbohydrate chains, which are attached to the proteins on the outer surface of the membrane. These carbohydrate chains help the cell recognize and communicate with other cells.