University:
Yeshiva University
Course:
BIO1011 | Biology Principles Lectures
Academic year:

2021
Views:

29

Pages:

2
Author:

Stevan J.

Biomembrane The function of biomembranes can be said to be a means of controlling the transfer and diffusion of ions or molecules, as a framework for the preparation of enzymes, a transport vehicle between cell organelles, a place for the formation of several macromolecules and as a source of information. Before explaining biomembranes, it would be better to explain membranes first. A membrane is a separation device in the form of a barrier that has selective properties which can separate two phases from various mixtures. The mixture can be a solid, liquid or gas which has homogeneous or heterogeneous properties. Driving force is something that causes a transport process on the membrane in the form of convection or diffusion of each molecule, as well as the attraction between charges or solution concentrations and also differences in temperature and pressure. A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates cells from the external environment or creates intracellular compartments. Biological membranes, in the form of eukaryotic cell membranes, consist of a phospholipid bilayer with embedded, integral and peripheral proteins used in communication and transport of chemicals and ions. Most of the lipids in cell membranes provide a fluid matrix for proteins to rotate and diffuse laterally for physiological functions. Proteins adapt to the high membrane fluidity environment of the lipid bilayer by the presence of annular lipid shells, which consist of lipid molecules tightly bound to the surface of integral membrane proteins. Cell membranes differ from insulating tissues formed by layers of cells, such as mucous membranes, basal membranes, and serous membranes. History of the Discovery of Biomembranes • • • 1895 - Ernest Overton hypothesizes that cell membranes are made from lipids. 1925 -Evert Gorter and François Grendel discovered that the membranes of red blood cells are formed by a lipid layer two molecules thick, i.e. they described the bilipid nature of cell membranes. 1935 - Hugh Davson and James Danielli proposed that lipid membranes are layers composed of proteins and lipids with a pore-like structure that allows specific permeability for certain molecules. Later, they suggested a model for the cell membrane, which consists of a lipid layer surrounded by protein layers on both sides (Beck. 1980). • • 1957 -J. David Robertson, based on electron microscope studies, established the "Unit Membrane Hypothesis". This states that all membranes in cells, namely plasma membranes and organelles, have the same structure: a double layer of phospholipids with a monolayer of proteins on either side. 1972 - SJ Singer and GL Nicolson proposed the fluid mosaic model as an explanation for recent data and evidence regarding the structure and thermodynamics of cell membranes.