What is the primary function of the cell membrane?

The primary function of the cell membrane is to regulate what enters and leaves the cell, making it vital for maintaining the cell's internal environment and overall homeostasis. The cell membrane is selectively permeable, which means it controls the movement of substances in and out of the cell based on size, polarity, and concentration gradients. This regulation allows the cell to take in essential nutrients, expel waste products, and maintain a stable concentration of ions and molecules, which is crucial for various cellular processes.

The structure of the cell membrane, primarily composed of a phospholipid bilayer embedded with proteins, facilitates this selective permeability. The proteins can function as channels or transporters that assist in the movement of specific substances across the membrane, while the lipid bilayer acts as a barrier to most water-soluble substances.

In contrast, the other options refer to separate functions that are not directly associated with the cell membrane. The storage of genetic information pertains to the nucleus, energy production is primarily associated with mitochondria, and protein synthesis occurs in ribosomes. These functions are essential for cellular activities but do not define the cell membrane's primary role.