Chapter 4 Biomembranes: Their Structure, Chemistry and Functions Learning objectives: 1. a brief history of studies on the structrure of the plasma membrane 2. Model of membrane structure: an experimental perspective 3. The chemical composition of membranes 4. Characteristics of biomembrane 5. An overview of the functions of biomembranes
Chapter 4 Biomembranes: Their Structure, Chemistry and Functions Learning objectives: 1. A brief history of studies on the structrure of the plasma membrane 2. Model of membrane structure: an experimental perspective 3. The chemical composition of membranes 4. Characteristics of biomembrane 5. An overview of the functions of biomembranes
1. a brief history of studies on the structrure of the a)L4n的nge p lasmic membrane A Conception Plasma membrane(cell membrane), Intracellular membrane, Biomembrane B. The history of study feud Albertson wf Fud mosac ◆ Overton(1890s): Lipid nature of PM
1. A brief history of studies on the structrure of the plasmic membrane A. Conception: Plasma membrane(cell membrane), Intracellular membrane, Biomembrane. B. The history of study Overton(1890s): Lipid nature of PM;
o Gortter and Grendel( 1925 ) The basis of membrane structure is a lipid bilayer To answer the question that how many lipid layers were in membrane, in 1925 Gorter and Grendel extracted the lipids from a known number of erythrocytes and spread the lipid film on a water surface. The area of lipid film on the water was about twice(.8-2.2)the estimated total surface area of the erythrocytes, so they concluded that the erythrocyte plasma membrane consisted of not one but two layers of lipids. O Cell physiologists(1920s and 1930s) The decrease in surface tensions of PM might be explained by the proteins
To answer the question that how many lipid layers were in membrane, in 1925 Gorter and Grendel extracted the lipids from a known number of erythrocytes and spread the lipid film on a water surface. The area of lipid film on the water was about twice(1.8-2.2) the estimated total surface area of the erythrocytes, so they concluded that the erythrocyte plasma membrane consisted of not one but two layers of lipids. Gortter and Grendel(1925): The basis of membrane structure is a lipid bilayer Cell physiologists(1920s and 1930s) : The decrease in surface tensions of PM might be explained by the proteins
◇ H. Dayson and danielli(1935):“ sandwich model Membranes also contain proteins If the membranes only consist of pure lipids, it could not explain all the properties of membranes. For example, sugars, ions, and other hydrophilic solutes move into and out of cells much more readily than could be explained by the permeability of pure lipid bilayers. To explain such differences, Davson and Danielli invoked the presence of proteins in membranes in 1935. The plasma membrane is composed of a lipid bilayer that is lined on both its inner and outer surface by a layer of globular proteins; in addition to, the presence of protein-lined pores for polar solutes and ions to enter and exit the cell
H.Davson and J.Danielli(1935): “sandwich model” Membranes also contain proteins. If the membranes only consist of pure lipids, it could not explain all the properties of membranes. For example, sugars, ions, and other hydrophilic solutes move into and out of cells much more readily than could be explained by the permeability of pure lipid bilayers. To explain such differences, Davson and Danielli invoked the presence of proteins in membranes in 1935. The plasma membrane is composed of a lipid bilayer that is lined on both its inner and outer surface by a layer of globular proteins; in addition to , the presence of protein-lined pores for polar solutes and ions to enter and exit the cell
◇ J.D. Robertson(1959) The TEM showing the trilaminar appearance of PM; Unit membrane model: O S.J. Singer and G Nicolson (1972): fluid-mosaic model ◇ K. Simons et a(1997) lipid rafts model Functional rafts in Cell membranes Nature387:569-572 that preposed ym出图k
J.D.Robertson(1959): The TEM showing:the trilaminar appearance of PM; Unit membrane model; S.J.Singer and G.Nicolson(1972): fluid-mosaic model; K.Simons et al(1997): lipid rafts model; Functional rafts in Cell membranes. Nature 387:569-572