Lipid bilayer

A DPPC bilayer simulation
Color scheme: PO4 = green, N(CH3)3 = violet, water = blue, terminal CH3 = yellow, O = red, glycol C = brown, chain C = grey (Larger Version)

A membrane or zone of membrane, which is like a biological membrane in structure and composition but lacking proteins. In other words, membrane composed only of lipid.

Within a critical range of concentrations, lipids alone in a test tube of water will self-organize to form a "bilayer." It is composed of two opposing layers of lipid molecules arranged so that their tails face one another to form the oily bilayer core, while their electrically charged or polar heads face the aqueous solutions on either side of the membrane.