What is the primary function of the plasma membrane?

The primary function of the plasma membrane is to regulate the movement of substances in and out of the cell. This selectively permeable barrier is crucial for maintaining homeostasis within the cell by controlling the internal environment. The plasma membrane is composed of a lipid bilayer with embedded proteins that assist in transporting molecules, signaling, and communication with the external environment.

This selectivity allows essential nutrients to enter the cell while keeping waste products and harmful substances out, which is vital for the cell's survival and function. Additionally, the plasma membrane plays a role in cell recognition and interaction with other cells, further emphasizing its importance in cellular processes. The other choices do not accurately reflect the primary function of the plasma membrane; they pertain to different cellular processes and functions.