Fluid Mosaic Model
 
The liquid-like properties of lipid liquid crystals are assimilated into this model for the structure of cell membranes and for the organization of its protein and lipid components. The concepts that underlie this model assume that integral membrane proteins are “a heterogeneous set of globular molecules, each arranged in an amphipathic structure, i.e. with the ionic and highly polar groups protruding from the membrane into the aqueous phase, and the nonpolar groups largely buried in the hydrophobic interior of the membrane” (1). In this model the membrane is perceived as a mosaic of a continuous phospholipid bilayer that is periodically interrupted by proteins randomly distributed throughout the bilayer. The phospholipid bilayer is considered a viscous solvent that allows the dissolved proteins to diffuse laterally within the plane of the membrane.
References
1 . S. J. Singer and G. L. Nicholson. (1972) Science 172, 720–731.