Which of the following is a special function of the plasma membrane?

The plasma membrane's primary role is to regulate the exchange of substances in and out of the cell. This semi-permeable barrier controls which molecules can pass through, thus maintaining the internal environment of the cell. The membrane is composed of a phospholipid bilayer embedded with proteins that facilitate the selective transport of ions, nutrients, and waste products.

This function is crucial for homeostasis, allowing cells to maintain optimal conditions for biochemical reactions. For example, the plasma membrane can open or close channels and transporters, enabling cells to absorb essential molecules while excluding harmful substances. In contrast, protein synthesis, energy production, and cell division are functions associated with other cellular structures. Protein synthesis occurs in the ribosomes, energy production primarily occurs in the mitochondria, and cell division is driven by mechanisms involving the nucleus and the cytoskeleton. Thus, the special function of the plasma membrane is aptly characterized by its role in regulating the exchange of substances.