细胞膜的结构和功能.ppt

1、第三节 细胞膜的结构和功能 The structure and function of cell membrane,3.1 细胞膜的结构 The structure of cell membrane 3.2 细胞膜的化学组成 Chemical components of cell membrane 3.3 细胞膜的分子结构与特点 Cell Membrane Molecular Structure and Characteristics 3.4 细胞膜的功能 The Functions of Cell Membrane,3. 1 细胞膜的结构 The structure of cell memb

2、rane,Cell membrane is a limiting membrane separates cytoplasm and surroundings ,also termed plasma membrane. Cell membrane has three-layered structure,1 bright band between 2 darks .,cell coat,lipid bilayer,transmembrane glycoprotein,adsorbed glycoprotein,extra-cellular space,glycolipid,cytosol,细胞表面

3、(cell surface),脂类 (lipids) 50% 蛋白质(proteins) 40%-50% 糖类 (Glycols) 1%-10%,3.2 细胞膜的化学组成 Chemical components of cell membrane,细胞膜 Cell membrane,The chemical composition of membranes,A. Membrane lipids,B. membrane proteins,C. membrane carbohydrates,glycoprotein glycolipid,膜脂(Lipids in bio-membrane) amph

4、ipathic molecules, consist of a polar(hydrophilic) head and a nonpolar (hydrophobic) end,磷脂(phospholipid) 膜脂(lipids) 胆固醇(cholesterol) 糖脂(glycolipid),The lipids of most membranes are the derivatives of glycerol 3-phosphate.Phosphoglycerides are classified according to the nature of their head group.,

5、磷脂(phospholipid),Phosphoglycerides(磷酸甘油脂),PC: phosphatidylcholine (卵磷脂） X=choline PE: phosphatidylethanolamine （磷脂酰乙醇胺） X=ethanolamine PS: phosphatidylserine（磷脂酰丝氨酸）=serine,胆固醇(cholesterol),The basic structure of steroids is a four-ring hydrocarbon. It is a amphipathic because its hydroxyl group can

6、 interact with water. Cholesterol is more abundant in the mammalian cell membrane.,糖脂(glycolipid),外周蛋白 (peripheral proteins ) 内在蛋白 (integral proteins ),Peripheral proteins, 20%-30%，localize in the cytosolic or the exoplasmic face of the plasma membrane.,Integral proteins ( tramsmembrane proteins), 7

7、0%-80%, consist of three domains: cytosolic domain,exoplasmic domain and transmembrane domain.,膜蛋白(Proteins in bio-membrane),蛋白质Proteins,proteins associate with the lipid bilayer,膜蛋白的功能 Membrane proteins have many functions,Transporters,Linkers,Receptors,Enzymes,膜糖(carbohydrate in bio-membrane),2%10

8、% in membrane depend on the difference of cells covalent combine with membrane proteins and form glucoproteins all membrane carbohydrate pitch on the outside of plasma membrane.,D-glucose(葡萄糖) D-galactose(半乳糖) D-mannose (甘露糖) L-fucose(海藻糖) N-acetyl-D-galactosamine(半乳糖胺) N-acetyl-glucosamine(葡萄糖胺),Se

9、veral kinds of carbohydrate for animals membrane,1)Improve the stability of membranes 2) Advance the fastness of proteinase in extracellular matrix 3) Help membrane proteins to form correct three-dimensional configure 4)Take part in cell signal recognition, cell adhension and cell junction 5)Correct

10、 position for transfer of new protein,膜糖的功能Function Of Membrane Carbohydrate,流动镶嵌模型（1972年 Singer 和 Nicolson）(The fluid mosaic model),3.3 细胞膜的分子结构与特点 Cell Membrane Molecular Structure and Characteristics.,The core lipid bilayer constructs the skeleton of the cell membrane; B. Membrane proteins associ

11、ated with the lipid bilayer, peripheral proteins or integral proteins; C. The two surfaces of cell membrane are asymmetric; D. exists in a fluid state, capable of dynamic movement.,1. Lamella Structure Model 2. Unit Membrane Model 3. Lipid rafts model,Some Other Cell Membrane Molecular Structure Mod

12、el,不对称性Asymmetry,冰冻蚀刻技术,膜脂不对称 (lipids asymmetry) 膜蛋白不对称 (proteins asymmetry) 膜糖不对称 (carbohydrate asymmetry),3.3 细胞膜的分子结构与特点 Cell Membrane Molecular Structure and Characteristics.,The two halves of the bilayer often contain different types of phospholipids and glycolipids. The proteins embedded in th

13、e bilayer have a specific orientation .,膜不对称性(Membrane Asymmetry),The asymmetry of membrane protein and glycoprotein,膜流动性(Membrane Fluidity),Membrane fluidity is essential for membrane function: Allows molecules to diffuse rapidly Helpful for cell movement, cell growth, cell division, secretion etc,

14、First demonstrated in 1970 by Larry Frye and Michael Lipids provide the matrix in which integral proteins of a membrane are embedded, thus the physical state of the lipid is important in determining the mobility of integral proteins.,First demonstrated in 1970 by Larry Frye and Michael Lipids provid

15、e the matrix in which integral proteins of a membrane are embedded, thus the physical state of the lipid is important in determining the mobility of integral proteins,温度影响膜脂的状态,Types of movement,1.Lateral diffusion(侧向扩散) 2. rotary motion(旋转运动) 3. swing left and right(左右摆动) 4. contraction movement(伸缩

16、运动) 5. reversed movement(翻转运动),影响细胞膜流动性的因素The factors that influences bilayer fluidity,The effects of fatty acid composition on membrane fluidity The length of the fatty acid The degree of unsaturation of fatty acid side chains The temperature The effects of sterols,3. 细胞膜的功能 The Functions of Cell M

17、embrane,1. Define the boundaries of the cell and its organelles. 2. Serve as loci for specific functions. 3. provide for and regulate transport processes. 4. contain the receptors needed to detect external signals. 5. provide mechanisms for cell-to-cell contact, communication ,adhesion.,3.1 物质运输 Sub

18、stance Transport,协助扩散(facilitat ed diffusion ),被动运输 (passive transport),吞噬(phagocytosis) 胞饮(pinocytosis) 受体介导的内吞作用(receptor mediated endocytosis）,简单扩散(simple diffusion),主动运输(active transport),穿膜运输 Transmembrane transport,胞吞(endocytosis),膜泡运输 Vesicle transport,胞吐(exocytosis),物质运输 (Substance Transport

19、）,Overview of trans-membrane transport,3.4.1.1 主动运输（Active transport ）,Mediated by a specific membrane proteins Against their concentration gradient Need the energy supply (ATP provide or indirect provide),3.4.1.2 被动运输（Passive diffusion）,简单扩散 (simple diffusion),协助扩散 ( Facilitated Diffusion),suggest

20、that such molecules can diffuse across cellular membranes without transport proteins.,no metabolic energy no specific transport proteins transport chemical concentration gradient,简单扩散 (simple diffusion),Many polar molecules, ions, such as glucose ,amino acid and water, transport across membrane with

21、 facilitated diffusion, a kind of protein-mediated movememt across a membrane.,no metabolic energy need specific transport proteins transport chemical concentration gradient,协助扩散（ Facilitated Diffusion ）,This micrograph was taken from Endocytosis,3.4.1.3 膜泡运输（vesicle transport）,受体介导的内吞作用(receptor me

22、diated endocytosis),吞噬(phagocytosis),3.4.2 信号传导 (signal transduction),细胞的信号分子及其受体 Signaling Molecules and Their Receptors 受体(receptor)： 细胞膜受体Cell Surface Receptors 细胞内受体Intracellular Receptors,生命的基本问题是信息问题 The basic problems of life are the information problems,Modes of cell-cell Signaling,Chemical components：glycoprotein, lipoprotein et al. 识别部位(recogniza