ABSTRACT
Electron microscopic analysis of the structure of cells led to the discovery of membranes as existing as discrete structural entities. The role of the proteins was to stabilize the lipid bilayer, and they were not considered to play any specific role by contributing to the permeability properties of the membrane. The evolution of membrane models reminds one in certain aspects of the evolution of year models of automobiles. The chapter provides different approaches that represent by different branches of evolutionary tree. The first branch is contributed by membrane models that have been developed on the basis of an objective evaluation of observations. The second model on this branch is that of J. Schlessinger and G. L. Nicolson that, presented in 1972, was based on a qualitative thermodynamic reasoning. The membrane is assumed to consist of a continuous lipid bilayer, and the ilayer is cleaved through its middle.
