《膜结构特性》PPT课件.ppt

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1、Medical Cell Biology,郑州大学基础医学院细胞、遗传学教研室程 晓 丽,You will start learning about how cells work by studying this introductory course.Since all organisms are made of cells,we need to understand what cells are and how they function.We also need to understand how they develop and how they comm-unicate with o

2、ne another to maintain the essential functions of the organism.,In recent years,spectacular advances have been made in our understanding of how cells work.Since cell biology is at the core of all life,it is one of the most active and exciting areas of current scientific research.,You are about to em

3、bark upon a most exciting journey,and this course is your ticket for the first part.Im very glade to discuss a few things with you before you start on your own trips.,Preface,Dear Students:,Preface,All of the information necessary is encoded in the DNA of each cell,and one of the major advances of r

4、ecent years has been the determination of the complete sequences of the DNA of many species,including humans,flies and some plants.The infor-mation encoded in the DNA is expressed in cells through the synthesis of messenger RNAs and proteins,and we now have powerful tools to allow us to determine si

5、multaneously the,amounts of the many thousands of messenger RNAs that are present in each cell,and our ability to analyze the patterns of protein expression is developing rapidly,especially through increased application of mass spectrometry to cell biology.,Preface,Learning about how individual prot

6、eins function and about how they interact in complex networks inside cells will keep us all busy for many more years.But the payoff is fantastic!Apart from the beauty of knowledge of how living organisms function for its own sake,the more we know the more we can apply the information to understandin

7、g the causes of the many diseases that continue to plague us,leading eventually to better therapies and even to cures for many of them.,While these tools have increased enormously what we can do,the hardest jobs still lie ahead.What does each protein do to help determine and support the functions of

8、 each of the many hundreds of different cell types that make up complex organisms such as us?,Preface,美国科学院院士、美国医学院、英国皇家科学院院士、美国克利夫兰医学中心莱纳研究所原所长、复旦大学荣誉教授、著名分子细胞生物和遗传学家George.R.Stark Professor,So,please take this first step on your journey seriously but with enjoyment and anticipation of all of the w

9、onders that will follow.Good luck!,The connection between cell biology and medicine is very tight,and the explosion in our current understanding of cell biology is already leading to major tools in the fights against cancer,heart disease,infectious disease and the other ailments from which humans su

10、ffer.,First part Introduction,Second part Cell membrane and Cell surface,Third part Cytoplasm and Orgenelle,Fourth part Nucleus,Fifth part Cell division and growth,Sixth part Cell engineering,What,we,will,study,？,Seventh part Status quo and uptrend,Chapter 1,Introduction,Cell Biology 是以发育与遗传的关系为研究核心

11、，从整体层次、亚显微结构层次、分子层次，以动态观点、细胞角度研究、阐明、控制并利用各种基本生命现象的变化与发展规律，以及核质之间、细胞之间、细胞与环境之间相互关系的一门科学。,NEW CONCEPTS,从生命结构层次来看，细胞生物学位于分子生物学和个体生物学之间，并同它们互相衔接、互相渗透。因此，细胞生物学是一门承上启下的学科，它与分子生物学一起同是现代生命科学的基础，并广泛渗透到遗传学、发育生物学、生殖生物学、神经生物学和免疫生物学等的研究中，和农业、医学、生物高新技术的发展有密切的关系，是生命科学的重要支柱之一。,NEW CONCEPTS,细胞生物学 是生命科学研究的基础，生命科学上的许多

12、基本问题必须在细胞中谋求解决，因此细胞生物学的研究目的不仅在于阐明各种生命活动的现象和本质，还必须进一步对这些现象的发展规律加以控制和利用，以达到为生产实践服务，造福于人类的目的。,NEW CONCEPTS,细胞形态学,细胞化学,细胞生理学,细胞遗传学,细胞生态学,细胞能力学,细胞动力学,cytomorphology,cytochemistry,cytophysiology,cytogenetics,cytoecology,cytoenergetics,cytodynamics,Cell biology,分类,细胞既是人体正常结构和功能的基本单位，也是病理发生的基本单位，细胞结构与功能的异常是

13、疾病发生的基本原因或结构基础。,细胞生物学与医学,Example,1.细胞的变性坏死-溶酶体-风湿性关节炎、痛风2.细胞的衰老与死亡-基因的编程性控制3.癌症的发生-(细胞的分裂、基因的编程性控制、c-myc、bcl-2、p53,恶病质)4.疾病的快速诊断-单克隆抗体（感染、癌）5.癌疫苗-细胞融合技术6.人工细胞7.细胞与中医的阴阳学说-cAMP(阴)和 cGMP(阳),Cell Membrane and Cell Surface,Secant Part,Membranous molecular structure and character,Cell surface and its spe

14、cial feature,Transportation of Cell Membrane,membrane and cell recognition,What,we,will,study,？,Chapter 5,Chapter 6,Chapter 7,Chapter 8,membrane receptor and cellular signal transduction,Chapter 9,从初步具有生命现象的蛋白质核酸复合体系，向活细胞进化所获得的重用形态特征，就是在生命物质的外表出现了一层膜相结构，即细胞膜，构成了最早的原始细胞。细胞膜的出现是生命物质由非细胞形态向细胞形态进化的重要转折。

15、,细胞的形成使生物体具有更大的相对独立性，并由此获得一个相对稳定的内环境，细胞通过膜有选择地从周围环境中摄取营养，排除代谢物，大大提高了原始生命与外界环境进行物质交换的水平，推动了细胞内物质向更高级形态分化，对生命本身的存在和进一步发展起有重要作用。,Introduction to Membrane,NEW CONCEPTS,Cell membrane is a fatty film so thin which surrounding cytoplasm outside and serve as barriers between the inside and the outside of th

16、e cell.It is also termed plasma membrane.,细胞膜 是围绕在细胞质外的一层很薄的膜，是区分细胞内外的界层，也称为质膜。,The membrane take the different methods to select the material that try to across the membrane.For all kind of life movement,membrane can ensure the environ-ment of inside stay in stable.,细胞膜以不同的方式对进出细胞内外的物质有选择作用.细胞膜可为生命

17、活动提供一个稳定的内环境.,Under the electron microscope,the plasma membrane has a three-layered appearance of two dark bands separated by a light zone.As a unite,the three-layered appearance are termed unit membrane.,高倍率电镜下，膜有三层结构组成，两层深色带，中间隔有一层疏松的浅色带，此三层结构作为一种单位，称为单位膜。,NEW CONCEPTS,biological membranes=Plasma

18、Membrane+Intracellular Membrane,生物膜形成的意义,生物膜是细胞进行生命活动的重要结构基础；对于细胞内环境稳定、能量转换、信息传递、物质交换等起重要作用；对细胞生存、生长、发育、分离、分化十分重要；在细胞间的相互识别、细胞与外部环境间的相互作用中起有主导作用,Chapter 5,The membranous molecular structure and character,Segment 1 The Chemical Component of Membrane,Segment 2 The Membranous Molecular Structure,Segmen

19、t 3 The Character of Membrane,The cellular plasma and organelle membranes within your body approximately contain 30%-80%lipid,20%-70%protein,2%-10%saccharide and inorganic(无机的)components.,二、Membrane proteins 膜蛋白,三、Membrane saccharide 膜糖类,Segment 1 The Chemical Component of Membrane,一、Membrane lipids

20、 膜脂,The different membrane have different components proportion.,一、Membrane Lipids,分 类：,1、磷脂(phospholipid,PL):,磷酸甘油酯 鞘磷脂(SM),2、胆固醇(cholesterol,C),3、糖脂(glycolipid,GL)：脑苷脂、神经节苷脂,animated model,Examples,phosphatidylcholine磷脂酰胆碱(卵磷脂),磷脂分子结构,磷脂酰乙醇胺 磷脂酰丝氨酸 磷脂酰胆碱 鞘磷脂,磷脂分子结构,流质的,粘性的,On the nature of the hyd

21、rocarbon tails:the closer and more regular the packing of the tails,the more viscous and less fluid the bilayer will be.,For this reason,lipid bilayers that contain a large proportion of unsaturated hydrocarbon tails are more fluid than those with lower proportions.,tight-knit form,full of free spac

22、e form,生物学功能,胆固醇分子结构,Cholesterol intercalates between the PLs,with its steroid ring and hydro-carbon tail parallel to the fatty acid chains of the PLs and perpendicular to the membrane surfaces.,animated model,Cholesterol 是坚硬、稳定的分子，通过其不饱和的尾的缠绕而填充在相邻磷脂分子当中，并因此能稳定双层脂膜，降低膜的流动性和水溶性物质的通透性。,生物学功能,糖脂分子结构,鞘

23、磷脂,Glycolipid are more minor components of human and other animal membranes.Sugar residues(糖基)of plasma membrane glycolipids almost always face the outside of the cell;that is,they have an asymmetric(不对称)distribution,being found only in the outer leaflet of the bilayer.,生物学功能,glycolipid：是膜的重要组成成分，参与

24、物质运输，细胞识别，免疫等一系列膜功能的完成。,膜脂的共同特征,兼性分子或双亲媒性分子(amphipathic molecule)即含有亲水的头又含有疏水的尾.其头部具有亲水性，尾部疏水且寻求与其他疏水分子相聚.,疏水环境的作用：使膜蛋白能够维持一定的空间构像，一些化学反应能顺利的进行；对极性物质的通透起屏障作用，可维持细胞内环境的相对稳定。,spherical liposome 球形脂质体,膜脂分子的物理特性,Integral/mosaic protein 膜内在/镶嵌蛋白,Peripheral/extrinsic protein 膜周边/外在蛋白,分类：,The proteins are

25、primarily for membrane functions,including transport of ions and polar molecules,binding of hormones,signal transduction across the membrane,and structural stabilization of the bilayer.,二、Membrane Proteins,Integral membrane proteins(膜嵌入蛋白)are embedded in the lipid bilayer.Peripheral membrane protein

26、(膜周边蛋白)associated by ionic interactions to an integral membrane protein.,integral/mosaic protein(内在蛋白),peripheral/extrinsic protein(周边蛋白),4.link with bilayer by covalent 以共价结合与脂双层结合,link with bilayer by noncovalent以非共价结合与脂双层结合,3.amphipathic molecular兼性分子；,solubility molecular可溶性分子；,2.link with bilay

27、er closely,airlessly or tightly 结合紧密；,1.more 含量多；,less 含量少；,Membrane proteins,Difference,link with bilayer unclosely,loosely,结合不紧密；,Multiple pass,镶嵌蛋白：通过非极性氨基酸部分直接与膜脂双层疏水区内的脂肪酸链共价结合而十分紧密地嵌在膜里。,Membrane ProteinsAssociate With the Lipid Bilayer Ways,Membrane ProteinsAssociate With the Lipid Bilayer Wa

28、ys,膜周边蛋白：通过静电作用、离子键、氢键与膜脂头部与膜内在蛋白的亲水部分相互作用而间接与膜结合,三、膜糖类,1、结构：一般由110个单糖或单糖衍生物(葡萄糖、葡萄糖胺、半乳糖、半乳糖胺、甘露糖、岩藻糖、唾液酸等)组成寡糖链(直链、分支链).,2、存在方式：以共价键结合在膜脂与膜蛋白上，形成糖脂(glycolipid)、糖蛋白(glycoprotein).,3、所有涉及细胞与环境有关的生理功能都与糖脂、糖蛋白有关。,ABO血型抗原是一种糖脂，其寡糖部分具有决定抗原特异性的作用。,例,Segment 2,membranes molecular structure,1902,Overton,细胞

29、膜由脂类构成,1925,Gorter等，膜由双层脂类构成,1935，Denielli等，片层结构模型,等,液态镶嵌模型,1975,Wallach,晶格镶嵌模型,1977,Jain 等,板块镶嵌模型,1959，Roberson，单位膜模型,现代 脂 筏 模 型,Lamella StructureModel片层结构模型,1930,with the realization that that biological membranes also contain protein,Danielli and Davison incorporated protein into the model of mem

30、brane that was called Lamella structure model.However,they visualized the protein as being attached to only the periphery of the membrane by association with the polar head groups of the phospholipids.蛋白质附着在膜内外磷脂分子极性头部表面.,“Three-decker structure”model,1959,J.D.Robertson高倍率电镜下发现，各种细胞膜和细胞内膜都有三层结构组成，两层

31、深色带，中间隔有一层疏松的浅色带，此三层结构作为一种单位，称为单位膜。Robertson认为内外两层深色的为蛋白质以折叠形式通过静电与中间浅色的磷脂结合。,Unit membrane model单位膜模型,Fluid mosaic model流动镶嵌模型,生物膜是球形蛋白质和脂类分子呈二维状态排列而成的非静止的、具流动性特点的一种结构。脂类双分子层既具有液态分子的流动性、又具有固体分子排列的有序性，流动的脂类双分子层构成的连续性膜性结构，各种球状蛋白质镶嵌脂类双分子层中，。,Freeze Etching Replica Technique,Various techniques have be

32、used to study cell membrane Fluid Mosaic Model such as the freeze form sample(冷冻制样),the freeze-fracture(冷冻断裂),the replica and shadowing(真空镀膜),especially the freeze etching and replicate(冰冻蚀刻复型)electron microscope techniques etc.,1.A membrane frozen rapidly to 1500C.2.Fractures with a cold knife,spli

33、tting the bilayer into the two leaflets.Integral membrane proteins are pulled to one leaflet or the other,leaving behind a pit.,(冰冻蚀刻复型技术),3.Deposition of carbon and heavy metal in thin layer on specimen surface(shadowing technique 真空镀膜)，a coat be made.4.The coating is thin enough to replicate detai

34、l of the exposed specimen surface.The metal replica,not the specimen itself,is used for micrographs(冰冻蚀刻复型).,Freeze Etching Replica Technique,观点：1、流动的脂双层构成膜的连续主体；流动性,有序性2、球状蛋白质镶嵌在脂双层中；分布不对称性,缺陷：不能解释流动性的质膜如何保持膜的相对完整性和稳定性。,Fluid mosaic model,Crystal mosaic model晶格镶嵌模型,生物膜中流动的脂质是不断的可逆的在无序的液态和有序的晶态之间相互转

35、变，即相变。膜内在蛋白对其周围的脂类分子具有控制作用，使其不能单独活动，这些脂类分子被称为界面脂(boundary lipid),脂质分子只在局部具有流动性。,1、有序结构板块被无序的流动板块分割；2、板块流动性不同。,Block Mosaic Model板块镶嵌模型,评论：晶格模型和板块镶嵌模型与流动镶嵌模型无本质区别只是对流动性的分子基础进行了补充。,Lipid Rafts Model脂筏模型,生物膜膜脂双分子层中富含胆固醇、鞘磷脂和蛋白质的区域 称为微区，由于鞘磷脂具有较长的饱和脂肪酸链，其分子间的作用力相对较强、结构较致密，微区结构域比膜的其他部分更有秩序、且流动较少，介于无序液体与液

36、晶之间，这些微区称为脂筏(lipid raft)。微结构域是鞘磷脂与胆固醇的动态集合，不同的脂筏上载有各自特异的蛋白质。,Cholesterol is enriched into lipid raft microdomains(dark blue)depicted amid the lipid bilayer(cyan and gray)of the cellular plasma membrane.Shown are two nitric oxide molecules(red and blue).The article by Miersch et al.,pages 1851318521,

37、details how cholesterol influences nitric oxide diffusion dynamics(yellow trails)and signaling.Cover art was created by Ethan Tyler,NIH Medical Arts Design Section.,Lipid Rafts Model,推测一个100m大小的脂筏可载有600个蛋白质分子；脂筏可以选择地接受某种蛋白质，它对特定的蛋白质的亲和性由胞内或胞外的刺激物调控.,脂筏可以不同程度地与膜内细胞骨架等蛋白质交联。,脂筏的功能:1)参与细胞信号转导;2）参与跨膜物质运

38、输。,Segment 3 The Features of the Cell Membrane,膜脂分布的不对称性膜蛋白分布的不对称性膜糖分布的不对称性,一、膜的不对称性,功能的方向性,一、膜的不对称性蛋白分布的不对称,The glycoproteins and glycolipids have an asymmetric(不对称的)distribution across bio-membrane.The sugar residues are always found on the non-cytoplasmic side of the membrane.,跨膜蛋白两亲水端的不对称分布,The

39、percent of lipids content,The significance of the asymmetric distribution?,Its allows the two sides of the membrane to be functionally distinct.,The lipids asymmetric distribution phenomenon had been verified by the biochemical quantitative analysis,一、膜的不对称性膜脂分布的不对称,不对称,膜内层和外层所含脂质分子的种类和含量不同；,膜内外磷脂层所

40、带电荷不同；,膜内外磷脂分子中脂肪的饱和程度不同；,糖脂均分布在外层脂质中；,膜蛋白的分布不对称以及跨膜蛋白两亲水端的不对称分布。,一、膜的不对称性膜脂分布的不对称,二、The fluidity of cell membrane 膜的流动性,1.The lipids fluidity-膜脂的流动性,相变(phase transition):液晶(liquid-crystal)态的脂质双层在生理温度下,不停地以各种方式运动,当温度降至某一点时,可从流动的液晶态转为晶态(或凝胶态glutinous)。温度升高时，晶态也可熔融为液晶态，这种变化称为相变，引起相变的这一温度为相变温度(phase tr

41、ansition temperature).,Membrane phospholipids are capable of several types of motion within the bio-membrane.Above the phase transition temperature,there are 5 different moving ways(在相变温度以上,膜脂分子有5种运动形式),The motion of phospholipids within the biological membrane.,1.The lipids fluidity-膜脂的流动性,Integral

42、 membrane proteins can also rotate(旋转)along their long axis within the membrane,but they do not flip-flop from one leaflet to the other.,2.The membrane proteins fluidity-蛋白质的流动性,Several lines of evidence have indicated that membrane proteins are also capable of lateral movement(侧向运动)within the plane

43、 of the membrane.,(There is a classic experiment to demonstrated that surface antigens of mouse and human cells ere capable of free diffusion).,Experiment demonstration the mixing of plasma membrane proteins on mouse-human hybrid cells,成帽反应,Diagram of gut epithelium showing how a membrane protein is

44、 restricted to a particular domain of the plasma membrane of an epithelial cell.,Protein A and B can diffuse laterally in their own membrane domains but are prevented from entering the other domain by a specialized cell junction called a tight junction.,Tight junction,例,胆固醇的影响：相变温度以上，增加膜脂的有序性；相变温度以下

45、可扰乱膜脂有序性。,脂肪酸链的长度和不饱和程度的影响；卵磷脂多鞘磷脂少流动性,影响膜流动性的因素,影响膜流动性的因素,膜蛋白的运动性受细胞内细胞骨架的控制,影响膜流动性的因素,1.胆固醇：胆固醇的含量增加会降低膜的流动性；2.脂肪酸链的饱和度：脂肪酸链所含双键越多越不饱和，使膜流动性增加；3.脂肪酸链的链长：长链脂肪酸相变温度高，膜流动性降低；4.卵磷脂/鞘磷脂：该比例高则膜流动性增加，是因为鞘磷脂粘度高于卵磷脂；5.其他因素：膜蛋白和膜脂的结合方式、温度、酸碱度、离子强度等；6.膜蛋白的运动性受细胞内细胞骨架的控制。,1.单位膜(unit membrane);兼性分子或双亲媒性分子(amph

46、ipathic molecule)?脂筏(lipid raft)？,3.画图并简要说明液态镶嵌模型,4.The character of the cell membrane 膜的特性？,6.膜脂、膜蛋白运动方式?,7.膜蛋白的存在方式?,2.液态/流动镶嵌模型?晶格模型?脂筏模型？,5.phase transition 相变？boundary lipid界面脂？,Key point,8.影响膜流动性的因素,细胞膜的功能,细胞质膜的主要功能概括如下：1.为细胞的生命活动提供相对稳定的内环境；2.选择性的物质运输，包括代谢底物的输入与代谢产物的排出；3.提供细胞识别位点，并完成细胞内外信息的跨膜传

47、递；4.为多种酶提供结合位点，使酶促反应高效而有序地进行；5.介导细胞与细胞、细胞与基质之间的连接；6.参与形成具有不同功能的细胞表面特化结构。,附加内容,脂筏（lipid raft）是质膜上富含胆固醇和鞘磷脂的微结构域（microdomain）。大小约70nm左右，是一种动态结构，位于质膜的外小页。由于鞘磷脂具有较长的饱和脂肪酸链，分子间的作用力较强，所以这些区域结构致密，介于无序液体与液晶之间，称为有序液体（Liquid-ordered）。在低温下这些区域能抵抗非离子去垢剂的抽提，所以又称为抗去垢剂膜（detergent-resistant membranes，DRMs）。脂筏就像一个蛋白

48、质停泊的平台，与膜的信号转导、蛋白质分选均有密切的关系。从脂筏的角度来看，膜蛋白可以分为三类：存在于脂筏中的蛋白质；包括糖磷脂酰肌醇锚定蛋白（GPI anchored protein），某些跨膜蛋白，Hedgehog蛋白，双乙酰化蛋白（doubly acylated protein）如：非受体酪氨酸激酶Src、G蛋白的G亚基、血管内皮细胞的一氧化氮合酶（NOS）；存在于脂筏之外无序液相的蛋白质；介于两者之间的蛋白质，如某些蛋白在没有接受到配体时，对脂筏的亲和力低，当结合配体，发生寡聚化时就会转移到脂筏中。脂筏中的胆固醇就像胶水一样，它对具有饱和脂肪酸链的鞘磷脂亲和力很高，而对不饱和脂肪酸链的亲

49、和力低，用甲基-环糊精（methyl-cyclodextrin）去除胆固醇，抗去垢剂的蛋白就变得易于提取。膜中的鞘磷脂主要位于外小页，而且大部分都参与形成脂筏。据估计脂筏的面积可能占膜表面积的一半以上。脂筏的大小是可以调节的，小的独立脂筏可能在保持信号蛋白呈关闭状态方面具有重要作用，当必要时，这些小的脂筏聚集成大一个大的平台，在那里信号分子（如受体）将和它们的配件相遇，启动信号传递途径。如致敏原（allergen）能够将过敏患者体内肥大细胞或嗜碱性细胞表面的IgE抗体及其受体桥联起来，形成较大的脂筏，受体被脂筏中的Lyn（一种非受体酪氨酸激酶)磷酸化，启动下游的信号转导，最终引发过敏反应。细胞

50、表面的穴样内陷（caveolae）具有和脂筏一样的膜脂组成，不含笼形蛋白（clathrin），含有caveolin（一种小分子量的蛋白，21KD）。大量存在于脂肪细胞、上皮细胞和平滑肌细胞。这种结构细胞的内吞有关，另外穴样内陷中还富含某些信号分子，说明它与细胞的信号转导有关。,细胞学发展萌芽阶段(sprouting period),细胞学说的创立阶段(origination period),经典细胞学阶段(classical period),实验细胞学阶段(experimental period),细胞生物学阶段(cell biological period),16世纪19世纪初,19世纪初