The primary component of most biological membranes is phospholipids. These molecules consist of a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails. In aqueous environments, phospholipids arrange themselves into a bilayer, creating a semipermeable membrane that separates the internal cellular environment from the external surroundings. This structure is crucial for maintaining cell integrity, facilitating selective transport of substances, and enabling communication with other cells. Proteins and carbohydrates embedded within this membrane further enhance its functionality and specificity.