Answer:
Phospholipids are important molecules in biological membranes. They have a polar (hydrophilic) head and two nonpolar (hydrophobic) tails. In membranes, phospholipids arrange themselves in a bilayer structure called the phospholipid bilayer. The hydrophilic heads face outward, interacting with the aqueous environments on both sides of the membrane, while the hydrophobic tails are oriented inward, avoiding water and interacting with each other. This bilayer forms the basis of cell membranes, providing a selective barrier for the cell and allowing the regulation of molecular and ion movement. Proteins are also embedded within this bilayer, contributing to various membrane functions.