細(xì)胞4,細(xì)胞膜與細(xì)胞表面-ppt課件

1、 磷脂磷脂A. 膜脂膜脂B. 膜蛋白膜蛋白 Bacteriorhodopsin consists largely of membrane-spanning a helices The transmembrane helices in multipass membrane proteins occupy specific positions in the folded protein structure that are determined by interactions between the neighboring helices. These interactions are cruci

2、al for the structure and function of the many channels and transporters that move molecules across lipid bilayers. Converting a single-chain multipass protein into a two-chain multipass protein. barrel Another structural motif common in membrane proteinssingle-pass transmembrane proteinsA transmembr

3、ane protein always has a unique orientation in the membrane. This reflects both the asymmetric manner in which it is inserted into the lipid bilayer in the ER during its biosynthesis and the different functions of its cytosolic and noncytosolic domains. These domains are separated by the membrane-sp

4、anning segments of the polypeptide chain.Membrane Proteins Often Function as Large ComplexesThe three-dimensional structure of the photosynthetic reaction center of the bacterium Rhodopseudomonas viridis.Solubilizing membrane proteins with a mild detergent. The detergent disrupts the lipid bilayer a

5、nd brings the proteins into solution as protein-lipid-detergent complexes. The phospholipids in the membrane are also solubilized by the detergent. The use of mild detergents for solubilizing, purifying, and reconstituting functional membrane protein systems. 共價(jià)銜接于外膜的膜脂和膜蛋白.1.3 膜的流動(dòng)性膜的流動(dòng)性沿膜平面的側(cè)向運(yùn)動(dòng)沿膜

6、平面的側(cè)向運(yùn)動(dòng) (107 times per second)脂分子圍繞軸心的自旋運(yùn)動(dòng)脂分子圍繞軸心的自旋運(yùn)動(dòng)脂分子尾部的擺動(dòng)脂分子尾部的擺動(dòng)雙層脂分子之間的翻轉(zhuǎn)運(yùn)動(dòng)雙層脂分子之間的翻轉(zhuǎn)運(yùn)動(dòng) (less than once a month for any individual molecule)膜脂的流動(dòng)性主要指脂分子的側(cè)向運(yùn)動(dòng)，主要取決于脂分子本身的膜脂的流動(dòng)性主要指脂分子的側(cè)向運(yùn)動(dòng)，主要取決于脂分子本身的組成及溫度。組成及溫度。影響膜流動(dòng)性的要素:(A)liposomes produced from a 1:1 mixture of phosphatidylcholine and sping

7、omyelin (B) liposomes produced from a 1:1:1 mixture of phosphatidylcholine, spingomyelin, and cholesterol.The lateral diffusion of membrane lipids can demonstrated experimentally by a technique called Fluorescence Recovery After Photobleaching (FRAP). The proteins can self-assemble into large aggreg

8、ates (A); they can be tethered by interactions with assemblies of macromolecules outside (B) or inside (C) the cell; or they can interact with proteins on the surface of another cell (D). Three domains in the plasma membrane of guinea pig sperm defined with monoclonal antibodies. 指細(xì)胞膜下與膜蛋白相連的由纖維蛋白組成的網(wǎng)架構(gòu)造，指細(xì)胞膜下與膜蛋白相連的由纖維蛋白組成的網(wǎng)架構(gòu)造，它參與維持細(xì)胞膜的外形并協(xié)助質(zhì)膜完成多種生理功能。它參與維持細(xì)胞膜的外形并協(xié)助質(zhì)膜完成多種生理功能。1.5 膜骨架膜骨架帶3蛋白和血型糖蛋白是膜整合蛋白，在維持細(xì)胞形狀上不起決議性作用，它們?yōu)槟す羌艿鞍滋峁┙Y(jié)合位點(diǎn)。血影蛋白和肌動(dòng)蛋白不是膜內(nèi)在蛋白，它們在維持膜的外形及固定其他膜蛋白的位置方面起重要作用。膜骨架蛋白主要包括血影蛋白，肌動(dòng)蛋白，錨蛋白和帶4.1蛋白等。 1.6 細(xì)胞膜的根本功能 1. 提供相對穩(wěn)定的內(nèi)提供相對穩(wěn)定的內(nèi)環(huán)境。環(huán)境。2. 選擇性的物質(zhì)運(yùn)輸選擇性的物質(zhì)運(yùn)輸和能量傳送。和能量傳送。 3. 提供細(xì)胞識