Cell membrane (plasma membrane) lipid bilayer

The **cell membrane** (also known as the **plasma membrane**) is a thin, flexible, semipermeable barrier surrounding all living cells, composed primarily of a **lipid bilayer** structure. The bilayer consists of two opposing sheets of amphipathic phospholipids: hydrophilic heads facing the aqueous environment inside and outside the cell, and hydrophobic fatty acid tails facing inward, creating a hydrophobic core. This architecture confers selective permeability: small nonpolar molecules (such as oxygen and carbon dioxide) can diffuse freely, while polar and charged molecules require passage through specialized membrane proteins (channels, transporters, pumps). The membrane's physical and biological properties are also shaped by embedded **cholesterol, proteins, and carbohydrates**. The **lipid bilayer** itself is universal to all cells and organelles, enables compartmentalization, maintains homeostasis, and mediates interactions with neighboring cells and the extracellular environment. Unlike proteins in the membrane, the bilayer itself is not a specific therapeutic target, though its integrity is critical for cell viability.

Other names

cell membraneplasma membranephospholipid bilayerlipid bilayer