Computer illustration of a cutaway view of the human cell membrane. The cell membrane is a complex part of the cell that controls what can get in and out of the cell. The membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of the cell. Shown are the lipid bilayer (green), transmembrane proteins (pink) with carbohydrate chains (pink trees), transmembrane protein channels (blue), intrinsic membrane proteins (yellow), receptor proteins (teal) and cytoskeletal elements (light blue chains).