Plasma membrane diagram: The plasma membrane is a protective barrier

The plasma membrane is a protective barrier that surrounds the interior of the cell. Also called the cell membrane, this structure is semi-porous and allows certain molecules in and out of the cell. It serves as a boundary by keeping the cell's contents inside and preventing them from spilling out. Both prokaryotic and eukaryotic cells have plasma membranes, but the membranes vary among different organisms. In general, plasma membranes consist of phospholipids and proteins. The plasma membrane, also known as the cell surface membrane or plasmalemma, defines the boundary of the cell. It is a phospholipid bilayer with embedded proteins that encloses every living cell. The plasma membrane, a flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell, is best described by using a structural model called the fluid mosaic model. According to this model, the molecular arrangement of the plasma membrane resembles an ever-moving sea of fluid lipids that contains a mosaic of many different proteins. Some proteins float freely like icebergs in the lipid sea, whereas others are anchored at specific locations like boats at a dock. The membrane ... In other words, a diagram of the membrane (like the one below) is just a snapshot of a dynamic process in which phospholipids and proteins are continually sliding past one another.