The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.The basic function of the cell membrane is to protect the cell from its surroundings.ell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including the cell wall, glycocalyx, and intracellular cytoskeleton. Cell membranes can be artificially reassembled.