What does the plasma membrane of a cell do?

The plasma membrane of a cell acts as a semi-permeable boundary, which is essential for maintaining the internal environment of the cell. This characteristic enables the membrane to regulate which substances enter and exit the cell, thereby facilitating nutrient absorption, waste removal, and the overall maintenance of homeostasis. The semi-permeable nature arises from the lipid bilayer structure of the membrane, which allows certain small or nonpolar molecules to pass through while blocking larger or charged substances.

In addition, the plasma membrane plays a crucial role in communication and signaling, allowing the cell to respond to changes in its environment. It contains various proteins that serve as receptors, channels, and transporters, further emphasizing its function in controlling cellular interactions and activities. Therefore, the plasma membrane is not only a barrier but also an active participant in cellular processes, primarily through its selective permeability.