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. The plasma membrane is a selectively permeable barrier composed primarily of a phospholipid bilayer along with proteins, cholesterol, and carbohydrates. This structure allows the membrane to regulate what enters and exits the cell, maintaining homeostasis.

For example, essential nutrients such as glucose can be taken in, while waste products can be expelled. The presence of various transport proteins aids in facilitating the movement of molecules, either passively or actively, ensuring that the cell can respond to its environment adequately.

In contrast, generating energy for the cell is primarily the role of organelles such as mitochondria, while structural support is primarily provided by the cytoskeleton and cell wall in some organisms. Storing genetic material is the function of the nucleus and other organelles associated with genetic processes, rather than the plasma membrane itself.