1. Regulating what enters and exits the cell: The cell membrane acts as a selective barrier, controlling the movement of substances in and out of the cell. This is crucial for maintaining the cell's internal environment and carrying out essential processes. It does this through a combination of passive and active transport mechanisms.

2. Cell signaling and communication: The cell membrane contains receptors that bind to specific molecules, triggering internal signaling pathways. This allows cells to respond to their environment, communicate with other cells, and coordinate activities within the organism.