In essence, it is the semipermeable membrane surrounding the cytoplasm of a cell. All cells are contained by a cell membrane that keeps the pieces inside. The cell membrane is not a solid structure. It is made of millions of smaller molecules that create a flexible and porous container. Proteins and phospholipids make up most of the membrane structure.
The cell membrane, also known as the plasma membrane, is a thin layer of lipid and protein molecules that surrounds the cell, separating the internal environment of the cell from the external environment. The cell membrane plays a crucial role in maintaining the integrity of the cell and controlling the movement of substances in and out of the cell.
The structure of the cell membrane is often described as a fluid mosaic, as it is composed of a bilayer of phospholipids with embedded proteins, carbohydrates, and cholesterol molecules. The phospholipids have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail, which creates a selectively permeable barrier that only allows certain substances to pass through.
The proteins embedded within the cell membrane serve a variety of functions, including transport of molecules across the membrane, cell signaling, and cell recognition. Some proteins span the entire thickness of the membrane, while others are attached to only one side.
The cell membrane is also equipped with various transport mechanisms, such as channels, pumps, and carriers, which enable the selective movement of molecules into and out of the cell. Some substances can move freely through the membrane, while others require the help of these transport mechanisms.
Overall, the cell membrane is a dynamic structure that plays a critical role in maintaining the internal environment of the cell and communicating with the external environment. It is essential for the survival and function of all types of cells.