复旦大学：《细胞生物学 Cell Biology》课程教学资源（PPT课件）第四章 生物膜的结构、化学和功能 Biomembranes：Their Structure, Chemistry and Functions

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

Membrane proteins and lipids can be confined to s specific domain lipid raft

2. Singer and Nicolson's model of membrane structure: The fluid-mosaic model is the central dogma"of membrane biology. A. The core lipid bilayer exists in a fluid state, capable of dynamic movement. B Membrane proteins form a mosaic of particles penetrating the lipid to varying degrees. (outside of cell) membrane protein The fluid mosaic glycoprotein Model, proposed in cholesterol 1972 by Singer and phospholipid Nicolson had two key features, both plasma implied in its name. (cytoplasm inside of cell

2. Singer and Nicolson’s Model of membrane structure: The fluid-mosaic model is the “central dogma” of membrane biology. A. The core lipid bilayer exists in a fluid state, capable of dynamic movement. B. Membrane proteins form a mosaic of particles penetrating the lipid to varying degrees. The Fluid Mosaic Model, proposed in 1972 by Singer and Nicolson, had two key features, both implied in its name

Carbohydrate chains Phospholipid Lipid-anchored membran Hydrophobic Plasma Hydrophilic Carbohydrate Integral chains membrane Peripheral nembrane Outer membrane Phospholipid (a)Fluid mosaic model of membrane b layer (7-nm) Phospholipid surface transmembrane NH, amino acids carbohydrate (b) An integral membrane protein c)An enlarged helical transmembrane segment glycoprotein) (20-30 amino acids)

3. The chemical composition of membranes A Membrane Lipids: The Fluid Part of the model o Membrane lipids are amphipathic. There are three major classes of lipids Phospholipids: Phosphoglyceride and sphingolipids Glycolipids Sterols( is only found in animals)

3. The chemical composition of membranes A. Membrane Lipids: The Fluid Part of the Model Phospholipids: Phosphoglyceride and sphingolipids Glycolipids Sterols ( is only found in animals) ❖Membrane lipids are amphipathic. ❖There are three major classes of lipids:

Composition of biomembrane Cell surface PM p Golgi Cytosol I ER ER 0000 Lumen Cholesterol PO Glycolipid PE SM○