What is the primary function of the plasma membrane?

The primary function of the plasma membrane is to control the movement of substances in and out of the cell. This selectively permeable barrier is essential for maintaining the internal environment of the cell, allowing it to regulate the entry of nutrients and the exit of waste products. The structure of the plasma membrane, composed of a phospholipid bilayer with embedded proteins, facilitates this control. Specific transport proteins within the membrane can facilitate the movement of particular molecules, while other mechanisms like diffusion, osmosis, and active transport help manage the concentration gradients of various substances.

In addition to its role in regulating substance movement, the plasma membrane also plays a crucial role in communication and signaling between cells through receptor proteins. While energy provision, genetic information storage, and protein synthesis are vital cellular functions, they are not the primary roles of the plasma membrane. Thus, the correct response accurately captures the essence of the plasma membrane's function within the cell.