What is the main function of the cell membrane?

The main function of the cell membrane is to regulate the transport of molecules in and out of the cell. The cell membrane, also known as the plasma membrane, is primarily composed of a phospholipid bilayer embedded with proteins. This structure is selectively permeable, meaning it controls what substances can enter or exit the cell based on size, charge, and solubility.

Transport mechanisms facilitated by the cell membrane include passive transport (such as diffusion and osmosis), which does not require energy, and active transport, which requires energy to move molecules against their concentration gradient. This regulation is essential for maintaining homeostasis within the cell, allowing it to carry out necessary functions while protecting it from harmful substances.

While the other functions mentioned—such as storing genetic information, energy production, and synthesis of ribosomes—are critical for cellular function, they are not the primary role of the cell membrane. The regulation of transport is thus the key function that allows a cell to interact appropriately with its environment.