Plasmalemma, also known as the cell membrane, is a vital component of all living cells. Synonyms for plasmalemma include plasma membrane, cell membrane, and cytoplasmic membrane. Additionally, some scientists refer to it as the phospholipid bilayer, as it is composed of two layers of lipids that regulate the movement of materials in and out of the cell. The plasmalemma also contains various proteins that perform essential functions such as transporting molecules and signaling between cells. While these terms are interchangeable, they all refer to the outermost boundary of a cell, responsible for protecting and maintaining the internal environment of the cell.