第三节 细胞膜的结构和功能The structure and function of cell membra

ne

3.1 细胞膜的结构The structure of cell membrane

3.2 细胞膜的化学组成化学组成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 membrane

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

lipidbilayer

transmembraneglycoprotein

adsorbedglycoprotein

extra-cellular space

glycolipid

cytosol

细胞表面细胞表面 (cell surface)(cell surface)

脂类 (lipids) 50%

蛋白质(proteins) 40%-50%

糖类 (Glycols) 1%-10%

3.2 细胞膜的化学组成化学组成Chemical components of cell mem

brane

细胞膜Cell membrane

The chemical composition of membranes

A. Membrane lipids  

  phospholipid

  cholesterol

glycolipid

B. membrane proteins    

C. membrane carbohydrates

glycoprotein

glycolipid

Integral membrane protein  peripheral membrane protein

lipid-anchored protein

膜脂 (Lipids in bio-membrane)

amphipathic 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.

磷脂 (phospholipid)

Phosphoglycerides(Phosphoglycerides( 磷酸甘油脂磷酸甘油脂 ))

PC: phosphatidylcholine ( 卵磷脂） X=cholinePE: phosphatidylethanolamine （磷脂酰乙醇胺） X=ethanolaminePS: phosphatidylserine （磷脂酰丝氨酸）Ｘ =serine

胆固醇 (cholesterol)

The basic structure of steroids is a four-ring hydrocarbon. It is a amphipathic because its hydroxyl group can 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), 70%-80%, consist of three domains: cytosolic domain,exoplasmic domain and transmembrane domain.

膜蛋白膜蛋白 (Proteins in bio-membrane)(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

TransportersLinkers

ReceptorsEnzymes

膜糖膜糖 ((carbohydrate in bio-membran in bio-membrane)e)

2%~10% 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 )

Several kinds of carbohydrate for animal’s membrane

1) Improve the stability of membranes2) Advance the fastness of proteinase in extracellular matrix3) Help membrane proteins to form correct three-dimensional configure4) Take part in cell signal recognition, cell adhension and cell junction5) Correct position for transfer of new protein

膜糖的功能膜糖的功能Function Of Membrane CarbohydrateFunction Of Membrane Carbohydrate

流动镶嵌模型（流动镶嵌模型（ 19721972 年 年 Singer Singer 和 和 NicolsoNicolsonn ）） (The fluid mosaic modelThe fluid mosaic model)

3.3 细胞膜的分子结构与特点Cell Membrane Molecular Structure and Characteristics.

A. The core lipid bilayer constructs the skeleton of

the cell membrane;B. Membrane proteins associated with the lip

id 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 Model2. Unit Membrane Model3. Lipid rafts model

Some Other Cell Membrane Molecular Structure Model

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 the bilayer have a specific orientation .

膜不对称性膜不对称性 (Membrane Asymmetry)(Membrane Asymmetry)

The asymmetry of membrane protein The asymmetry of membrane protein and glycoproteinand glycoprotein

膜流动性膜流动性 (Membrane Fluidity)(Membrane Fluidity)

Membrane fluidity is essential for membrane function: Allows molecules to diffuse rapidly Helpful for cell movement, cell

growth, cell division, secretion etc

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 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

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( 伸缩运动 ) 5. reversed movement( 翻转运动 )

影响细胞膜流动性的因素影响细胞膜流动性的因素The factors that influences bilayer The factors that influences bilayer

fluidityfluidity

The effects of fatty acid composition on membrane fluidity

The length of the fatty acidThe degree of unsaturation of fatty acid si

de chainsThe temperatureThe effects of sterols

3.3. ４ 细胞膜的功能４ 细胞膜的功能 ThThe Functions of Cell Membranee Functions of Cell Membrane

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. ４ .1 物质运输　 Substance 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 (recepto

r mediated endocytosis ）

简单扩散 (simple diffusion)

主动运输 (active transport)

穿膜运输Transmembrane trans

port

胞吞 (endocytosis)膜泡运输Vesicle transport 胞吐 (exocytosis)

物质运输 物质运输 (Substance Transport(Substance Transport ））

Overview of trans-membrane transportOverview of trans-membrane transport

Property Passive Diffusion

Facilitated Diffusion

Active Transport

Specific transport protein

No Require Require Require

transport against its gradient

No No yes

Coupled to ATP hydrolysis

No No yes

Driven by movement of a ion down its gradient

No yes No

Examples O2, CO2, steroid hor- mones

Glucose and amino , ions and water

Ions, small hydrophilic molecules, lipids

3.4.1.1 3.4.1.1 主动运输（主动运输（ Active transportActive transport ））

Mediated by a specific membrane proteinsAgainst their concentration gradient Need the energy supply (ATP provide or

indirect provide)

Light

electrochemical gradient

Light powered pump

3.4.1.23.4.1.2 被动运输（被动运输（ Passive diffusionPassive diffusion ））

简单扩散 (simple diffusion)

协助扩散 协助扩散 ( Facilitat( Facilitated Diffusion)ed Diffusion)

suggest that such molecules can diffuse across cellular membranes without transport proteins.

O2, CO2 ,urea and ethanol,steroid hormones, drugs

Can diffuse across an artificial membranes

no metabolic energyno 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 facilitated diffusion, a kind of protein-mediated movememt across a membrane.

no metabolic energyneed specific transport proteins transport chemical concentration gradient

协助扩散（ 协助扩散（ Facilitated DiffusionFacilitated Diffusion ））

This micrograph was taken from Endocytosis

3.4.1.33.4.1.3 膜泡运输（ vesicle transport ）

受体介导的内吞作用 (receptor mediated 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 informat

ion problems

Modes of cell-cell

Signaling

Chemical components ： glycoprotein, lipoprotein et al.

识别部位 (recognization unit)

转换部位 (transmission unit)

效应部位 (effect unit)

结构 structure

受体 (Receptor)

　　　 特异性 (specificity)

高亲和性 (high affinity)

饱和性（ saturation)

　　 可逆性（ reversibility)

生理效应（ physiological response)

受体与配体作用特性 The action characteristics between the receptor and ligand

膜受体类型 ( The types of membrane receptors)

1.离子通道偶联的受体 Ion channel -linked receptor

2. G 蛋白偶联的受体 G protein- linked receptor

3. 与酶连接的受体 / 催化性受 Enzyme- linked receptor

3.4.3 细胞识别 （ cell recognition ）

Cell reaction caused by cell recognition

1. Cause signaling molecules enter the cell

2. Cause the cell adhesion

3. Cause the information transmembrane

transport

cell recognitioncell recognition is the interaction between cells that is possibly dependent upon specific adhesion .

细胞识别方式 Cell recognition mode