What is the primary function of the cell membrane?

The primary function of the cell membrane is to maintain homeostasis. The cell membrane acts as a selective barrier that regulates what enters and exits the cell, thereby helping to maintain a stable internal environment despite changes in the external environment. This selective permeability ensures that essential nutrients can enter the cell while waste products and potentially harmful substances are kept out or expelled.

By controlling the movement of substances, the cell membrane plays a crucial role in maintaining the proper balance of ions, nutrients, and water within the cell, which is vital for the cell's overall function and survival. This regulatory function contributes to the homeostasis of the organism as a whole, ensuring that cells can perform their necessary biological processes efficiently.

In contrast, other options such as energy production, protein synthesis, and genetic replication refer to specific functions that take place within the cell but are not the main role of the cell membrane itself.