The major driving force for formation of membrane lipid bilayer is

The molecules align themselves to form monolayers with the polar heads pointing in one direction and the nonpolar tails in the opposite direction (Figs 7.7A and B). Only fatty acids with more than 6 carbon atoms form monolayers. This explains their role as components of biomembranes The self-assembly of phospholipids into bilayers is driven by hydrophobic interaction. They also act as detergents and emulsifying agents. In vivo, they act as pulmonary surfactants.Ref: DM Vasudevan, page no: 79