Lipid bilayer

When lipids are together they spontaneously form a lipid bilayer due to their amphiphatic nature. Lipids consist of a 'head' and a 'tail' section. The 'tail' is hydrophobic and will group together in the center of the bilayer and the hydrophilic heads will form the edges of the bilayer protecting the 'tails' from contact with water.  There are 3 main classes of lipids used in the forming of a lipid bilayer for function a s a membrane: phospholipids; glycolipids and cholestral. The lipid mostly used for membranes is the phospholipid. In all lipids the 'tail' is formed from hydrocarbon chains, varying in length and saturation. In phospholipids the 'head' is formed from a phosphate attached to an alcohol and a 'platform' either glycerol or sphingosine, giving the lipid it's hydrophillic properties.

The lipid bilayer is seen as the universal basis for membrane structure. It can be seen using electron microscopy. However, to reveal the details of its organisation, specialised techniques such as freeze-fracture electron microscopy and and x-ray diffraction are required.