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

2. 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. The structure 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 .

4. 细胞表面(cell surface) cell coat lipid bilayer adsorbed glycoprotein
transmembrane
glycoprotein
cell coat
extra-cellular space
glycolipid
lipid
bilayer
cytosol

5. Chemical components of cell membrane
3.2 细胞膜的化学组成
Chemical components of cell membrane
脂类 (lipids) %
蛋白质(proteins) 40%-50%
糖类 (Glycols) %-10%
细胞膜
Cell membrane

6. The chemical composition of membranes
  phospholipid
  cholesterol
glycolipid
A. Membrane lipids  
Integral membrane protein
  peripheral membrane protein
lipid-anchored protein
B. membrane proteins    
glycoprotein
glycolipid
C. membrane carbohydrates

7. 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)

8. 磷脂(phospholipid)
The lipids of most membranes are the derivatives of glycerol 3-phosphate.Phosphoglycerides are classified according to the nature of their head group.

9. 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）Ｘ=serine

10. 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.

11. 糖脂(glycolipid)

12. 膜蛋白(Proteins in bio-membrane)
外周蛋白 (peripheral proteins )
内在蛋白 (integral proteins )
蛋白质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.

13. proteins associate with the lipid bilayer

14. Membrane proteins have many functions
膜蛋白的功能
Membrane proteins have many functions
Transporters
Receptors
Enzymes
Linkers

15. 膜糖(carbohydrate in bio-membrane)
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.

16. Several kinds of carbohydrate for animal’s 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)

17. 膜糖的功能 Function Of Membrane Carbohydrate
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 position for transfer of new protein

18. Cell Membrane Molecular Structure and Characteristics.
3.3 细胞膜的分子结构与特点
Cell Membrane Molecular Structure and Characteristics.
流动镶嵌模型（1972年 Singer 和 Nicolson）(The fluid mosaic model)
The core lipid bilayer constructs the skeleton of
the cell membrane;
B. Membrane proteins associated 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.

20. Some Other Cell Membrane Molecular Structure Model
1. Lamella Structure Model
2. Unit Membrane Model
3. Lipid rafts model

21. 膜脂不对称 (lipids asymmetry) 膜蛋白不对称 (proteins asymmetry)
3.3 细胞膜的分子结构与特点
Cell Membrane Molecular Structure and Characteristics.
膜脂不对称 (lipids asymmetry)
膜蛋白不对称 (proteins asymmetry)
膜糖不对称 (carbohydrate asymmetry)
不对称性Asymmetry
冰冻蚀刻技术

22. 膜不对称性(Membrane Asymmetry)
The two halves of the bilayer often contain different types of phospholipids and glycolipids.
The proteins embedded in the bilayer have a specific orientation .

23. The asymmetry of membrane protein and glycoprotein

24. 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

25. 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.

26. 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

27. 温度影响膜脂的状态

28. 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)

29. 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

30. 3.４ 细胞膜的功能 The 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.

31. 3.４.1 物质运输
　Substance Transport

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

33. Overview of trans-membrane transport
Property
Passive Diffusion
Facilitated Diffusion
Active Transport
Specific transport protein
No Require
Require
transport against its gradient No
yes
Coupled to ATP hydrolysis
Driven by movement of a ion down its gradient
Examples
O2, CO2, steroid hor- mones
Glucose and amino , ions and water
Ions, small hydrophilic molecules, lipids

34. 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)
Light
electrochemical gradient
Light powered pump

35. 3.4.1.2 被动运输（Passive diffusion）
简单扩散 (simple diffusion)
协助扩散 ( Facilitated Diffusion)

36. 简单扩散 (simple diffusion)
O2, CO2 ,urea and ethanol,steroid hormones, drugs
Can diffuse across an artificial membranes
suggest that such molecules can diffuse across cellular membranes without transport proteins.
no metabolic energy
no specific transport proteins
transport chemical concentration gradient

37. 协助扩散（ Facilitated 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 energy
need specific transport proteins
transport chemical concentration gradient

38. 3.4.1.3 膜泡运输（vesicle transport）
This micrograph was taken from Endocytosis

39. 受体介导的内吞作用(receptor mediated endocytosis)

40. 吞噬(phagocytosis)

41. (signal transduction)
信号传导
(signal transduction)

42. 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

43. 生命的基本问题是信息问题 The basic problems of life are the information problems

44. Modes of
cell-cell
Signaling

45. 受体(Receptor)
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

46. 受体与配体作用特性 The action characteristics between the receptor and ligand
　　　 特异性(specificity)
高亲和性(high affinity)
饱和性（saturation)
　　 可逆性（reversibility)
生理效应（physiological response)

47. 膜受体类型( The types of membrane receptors)
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

49. 细胞识别
（cell recognition ）

50. cell recognition is the interaction between cells that is possibly dependent upon specific adhesion .
Cell reaction caused by cell recognition
1. Cause signaling molecules enter the cell
2. Cause the cell adhesion
3. Cause the information transmembrane
transport

51. 细胞识别方式 Cell recognition mode

52. THAT’S ALL！