What is the primary function of the cell membrane?

The primary function of the cell membrane is to regulate the movement of substances in and out of the cell. This selectively permeable barrier is crucial for maintaining the internal environment of the cell, which is vital for its proper functioning. The cell membrane consists of a phospholipid bilayer with embedded proteins that facilitate various forms of transport. This includes passive processes like diffusion, as well as active transport mechanisms that require energy to move substances against their concentration gradient.

By controlling which molecules can enter or exit, the cell membrane helps maintain homeostasis, allowing the cell to respond to changes in its surroundings, obtain necessary nutrients, and expel waste products. Thus, the ability of the cell membrane to regulate substance movement is central to the overall health and functionality of the cell, making it a fundamental aspect of cellular life.