The plasma membrane, also known as the cell membrane, controls what enters and leaves the cell. It is selectively permeable, meaning it allows certain substances to pass through while preventing others from entering or exiting the cell. The plasma membrane contains various proteins and phospholipids arranged in a fluid mosaic structure, which creates a barrier and regulates the movement of molecules in and out of the cell. This control of substances entering and leaving the cell is crucial for maintaining proper cellular function and homeostasis.
