The current view of how the structure is based of the fluid mosaic model , which was made by S.J. Singer and G. L. Nicolson. The membrane structure is based on a double layer of lipid molecules, referred to as the bilayer , which have hydrophilic and hydrophobic parts. The hydrophilic parts face the polar environments at the membrane surfaces, and the hydrophobic portions which are in the membrane's interior, create a barrier preventing free movement of polar molecules across the membrane. The bilayer is in a fluid state, which means the lipid molecules in the bilayer are free to exchange places and rotate or undergo different motions associated with fluids. The segregating of the membrane into separate distinct regions, some which are occupied by lipids and other by proteins, is the mosaic part of the model.
All biological membranes contain both lipids and proteins.
Based on a glycerol framework, responsible for most of the bilayer structure. Glycophorin Glycophorin, a membrane glycoprotein, contains a single block of hydrophobic amino acids which span the entire membrane. The picture above shows the distribution of amino acids and sugars in glycophorin. Bacteriorhodopsin Bacteriorhodsin, dealing with the light absorption, contains seven alpha-helical transmembrane segments which span the membrane. Each is connected to the next by a loop of hydrophilic amino acids which extend into or through the polar membrane surfaces.