<P> When integral proteins of the lipid bilayer are tethered to the extracellular matrix, they are unable to diffuse freely . Proteins with a long intracellular domain may collide with a fence formed by cytoskeleton filaments . Both processes restrict the diffusion of proteins and lipids directly involved, as well as of other interacting components of the cell membranes . </P> <P> Septins are a family of GTP - binding proteins highly conserved among eukaryotes . Prokaryotes have similar proteins called paraseptins . They form compartmentalizing ring - like structures strongly associated with the cell membranes . Septins are involved in the formation of structures such as, cilia and flagella, dendritic spines, and yeast buds . </P> <Ul> <Li> 1895--Ernest Overton hypothesized that cell membranes are made out of lipids . </Li> <Li> 1925--Evert Gorter and François Grendel found that red blood cell membranes are formed by a fatty layer two molecules thick, i.e. they described the bilipid nature of the cell membrane . </Li> <Li> 1935--Hugh Davson and James Danielli proposed that lipid membranes are layers composed by proteins and lipids with pore - like structures that allow specific permeability for certain molecules . Then, they suggested a model for the cell membrane, consisting of a lipid layer surrounded by protein layers at both sides of it . </Li> <Li> 1957--J. David Robertson, based on electron microscopy studies, establishes the "Unit Membrane Hypothesis". This, states that all membranes in the cell, i.e. plasma and organelle membranes, have the same structure: a bilayer of phospholipids with monolayers of proteins at both sides of it . </Li> <Li> 1972--SJ Singer and GL Nicolson proposed the fluid mosaic model as an explanation for the data and latest evidence regarding the structure and thermodynamics of cell membranes . </Li> </Ul> <Li> 1895--Ernest Overton hypothesized that cell membranes are made out of lipids . </Li>

List 5 discoveries in the development of the fluid mosaic model of membranes
find me the text answering this question