A membrane is a semipermeable barrier between two distinct compartments that allows certain molecules, ions, or compounds to pass through it while barring select substances from passing. It plays an essential role in vital processes within all living organisms, from controlling the flow of chemicals to regulating the passage of vital nutrients into and out of cells. Membranes are made up of a variety of complex molecules, such as lipids and proteins, which are linked together to form a protective coating. By doing so, they are able to selectively exert control over the transport of biological molecules.

See also: emergence, evolution, proto b, prigogine, crypto