Lipid's three-dimensional molecular changes in cellular membrane and its relation with Endocytosis and Exocytosis

All the Lipids within the cellular membranes are existed in bilayer structure, but it has been proved that when some of these Lipids extracted from the native membrane and dispersed in water, it does exhibit non-bilayer structure, although the same Lipids have got bilayer structure in the membrane itself. It has been reported that some factors such as, enzymes (Lipase), temperature, change of pH and presence of some ions, some biochemical, biophysical and physiological variation, can convert the bilayer forming Lipids into the non-bilayer structure within the native membrane itself. Endocytotic vesicles are generated when segments of plasma membrane invaginated enclosing a minute volume of extracellular fluid and its contents. In exocytosis also remodeling of membrane is involved and most cells release macromolecules to the exterior by exocytosis, the processes of diffusion also happen with some Lipids change into the non-bilayer structure. The question that represent the subject of this review article is the way the Lipids in cellular membrane change their molecular structure from the bilayer to non-bilayer structure, to pave the way for the above processes.