The cell membrane is the name given to the phospholipid bilayer which surrounds cells. They control what compounds can move into and out of the cell.
Membranes are composed of a phospholipid bilayer, two sheets of phospholipid molecules made up of a hydrophilic head attached to a hydrophobic fatty acid tail. phospholipids do not form rigid shapes, instead acting more like a fluid. In the cells interior, membranes play an important role in the separation of distinct cellular processes in the form of organelles. Importantly, membranes enable chemical gradients, such as pH or proton gradients, to be established. chemical gradients power many of the cellular processes crucial for cellular processes such as energy production. The exterior cell membrane controls entry and exit to the cell. Selective protein import is required as imported proteins play key roles in cell signalling processes such as immune response stimulation and inhibition.