What role does the cell membrane play in a cell?

The cell membrane, also known as the plasma membrane, serves a crucial function in maintaining the internal environment of the cell by controlling what enters and exits. It is selectively permeable, meaning it regulates the passage of substances based on their size, charge, and solubility. This selective permeability helps the cell maintain homeostasis, allowing it to retain necessary nutrients and expel waste products effectively.

The cell membrane is composed of a phospholipid bilayer with embedded proteins that assist in the transport of materials across the membrane. Some proteins act as channels or carriers, facilitating the movement of specific ions and molecules, while other proteins serve as receptors that respond to signals from the environment.

In contrast, the other roles listed in the choices do not pertain to the cell membrane. Storing genetic information is primarily the function of the nucleus and DNA. Producing energy from glucose is mainly carried out by the mitochondria, where cellular respiration occurs. Lastly, packing proteins for transport is a function of the endoplasmic reticulum and Golgi apparatus, which modify and prepare proteins for distribution within the cell or for export outside the cell. Thus, while all these cellular activities are vital, the cell membrane's primary responsibility is to regulate the internal and external cell environment