Final answer:
The plasma membrane of a cell is composed of phospholipids arranged in a bilayer. The hydrophilic heads of the phospholipids face towards the outside of the cell and the cytoplasm, while the hydrophobic fatty acid tails are located in the interior of the membrane.
Step-by-step explanation:
The plasma membrane of a cell is primarily composed of phospholipids arranged in a bilayer. The hydrophilic heads of the phospholipids face towards the outside of the cell and the cytoplasm, while the hydrophobic fatty acid tails are located in the interior of the membrane. This hydrophobic region acts as a barrier to water and other polar molecules.