Cells form the basic unit of life and the universal feature of all cells is an outer selectively permeable membrane called the plasma membrane. Also, almost all eukaryotic cells contain complicated systems of internal membranes which give rise to various membrane-enclosed compartments within the cell. Structurally, cell membranes are composed of lipids and proteins. The Plasma Membrane All membrane proteins are located at the membrane, they are both structurally and functionally diverse. Every biological membrane has the same basic phospholipid bilayer structure associated with a set of membrane proteins that enables the membrane to carry out its individual activities Integral Membrane Proteins Integral membrane proteins, also called intrinsic proteins, have one or more parts that are embedded in the phospholipid bilayer. Many of the proteins associated with the plasma membrane are tightly bound to it. Peripheral Membrane Proteins Membrane proteins are often restricted in their movements. Since the lipid bilayer is indeed a film of oil, there is possibility of the structures immersed in it would be relatively free. Except for some membrane proteins, the mobility of other proteins is limited.. I found this topic on www.examville.com

There really important structure between cells, because they communicate the rest of the environment back to the cell so it can act accordingly.