Final answer:
The cell membrane is mainly composed of a phospholipid bilayer consisting of hydrophilic heads and hydrophobic tails.
Step-by-step explanation:
The cell membrane is primarily composed of a phospholipid bilayer. This means that it consists of two layers of phospholipid molecules. Each phospholipid molecule has a hydrophilic head that loves water and two hydrophobic tails that dislike water. The hydrophilic heads face outwards towards the cytoplasm and the fluid that surrounds the cell, while the hydrophobic tails are on the interior of the membrane.