字幕制作、校对：杨松鹏
当红细胞被强有力的血流高速运输时
白细胞则在血管壁的内皮细胞上缓慢滚动
这时，内皮细胞上的P选择蛋白
与白细胞上的一种糖蛋白PSGL-1相结合。
白细胞之所以能在血管壁的内皮细胞上滚动
就是因为这种结合的不断被破坏与重建
而这两种覆盖在各自细胞上蛋白的胞外结构域
在细胞周质的延伸，使得这种作用成为可能
磷脂双分子层的外叶含有丰富的鞘磷脂和磷脂胆碱
富含单层磷脂的脂筏浮在双分子层上
可以在其周围募集一些特定的膜蛋白
脂筏的刚性决定于附着在鞘磷脂的直链周围的胆固醇分子
脂筏以外，扭曲的不饱和烃链
以及较低的胆固醇浓度导致了膜流动性的增加
一旦侦测到信息，由内皮细胞分泌并与HSPG结合的
趋化因子就被呈递给白细胞的由7个跨膜区构成的受体
这种粘附刺激白细胞并引发了细胞内的级联通讯反应
磷脂双分子层的内叶在构成上与外叶有很大不同
其中一些蛋白质横贯质膜
其它则通过共价连接脂肪酸或一个与膜蛋白的非共价作用
将自己锚定在内叶上
膜连接蛋白复合体是跨膜信号传递中至关重要的部分
在膜双分子层上，血影蛋白被构建成六边形的网状结构 The beneath lipid bilayer,spectrin tetramers arranged into hexagonal network
并被膜蛋白锚定 that are anchored by membrane proteins
这种网状结构组成了细胞膜的骨架 This network forms the membrane skeleton
增强了细胞膜的稳定性并对膜蛋白的分布起重要作用 that contributes to membrane stability and membrane protein distribution
细胞骨架由网状结构的微丝蛋白构成 The cytososkelecton is comprised of networks of filamental proteins
这些蛋白质是细胞中特殊组织形成的原因 that are responsible for the special organization of cytosoltic components
在微丝内部，肌动蛋白的丝状结构成了平行的束状纤维 Inside the microvilli,actin filaments form type parallel bundles
并由横向交联的蛋白纤维加固 which are stabilized by cross-linking proteins
在细胞质的更深层，肌动蛋白的网络演变成钳口状结构 While deeper in the cytosome,the actin networks adapt jawlike structure
并被多种微丝结合蛋白加固 stabilized by a variety of actin binding proteins
微丝依靠蛋白复合体稳定其负端 Filaments kep their minus-ends by protein complex
并通过在其正端添加肌动蛋白聚合体向远离质膜的方向生长 grow away from plasma membrane by the addition of actin polymers to the plus-end
肌动蛋白的网络是一个高度动态的结构 The actin network is a very dynamic structure
伴随着持续不断的定向聚合和解聚合 with continuous directional polymerization and disassembly
切割蛋白可以引起微丝的断裂而形成较短小的微丝 Severing proteins induce kinks in the filaments and led to the formation of short filaments
并迅速解聚或者再聚合成新的微丝 that rapidly depolymerize or give rise to new filaments
细胞骨架还包括微管构成的网络 The cytososkeleton includes a network of microtubules
它们由微管蛋白异二聚体头尾相接成原纤维 created by lateral association of protofilaments formed with the polymerization of tubulin dimers
当某些微管的正端向质膜的方向延伸时 While the plus-ends of some microtubule extend toward the plasma membrane
蛋白质在其它微管上保持着各种构象间的平衡 protein stabilizes the curve conformation of protofilaments from other microtubules
使微管的正端快速解聚 causing the rapidly plus-end depolymeriztion
微管为运输泡的来回运输提供运输轨道 Microtubules provide tracts along which membrane bounded vesicles travel to and from the plasma membrane
这些运输泡的定向运输应归功于一族马达蛋白 The directional movement of these cargo vesicles is due to a family of motor proteins linking vesicles and microtubules
线粒体等膜结构细胞器被松散的束缚在细胞骨架上 Membrane bounded organelles like mitochondria are loosely trapped by the cytoskeleton
线粒体不断改变它的形状并与微管相互作用部分地改变其方位 Mitochondria change shape continuously and their orientation is partly dictated by their interaction with microtubules
所有的微管都由中心体延伸而出 All the microtubles originate from the centrosome
中心体有一对分开的有纤维结构的中心粒，位于细胞核附近 a distinct fiber structure containing two centrioles and located near the cell nucleus
核膜上的核孔允许少量mRNA和蛋白质进入细胞质 Pores in the nuclear envelope allow the import particles containing mRNA and proteins into the cytosol
这里，游离核糖体将信使RNA翻译为蛋白质分子 Here free ribosomes translate the mRNA molecules into proteins
这其中有的蛋白质分子将留在细胞质中 Some of these proteins will reside in the cytosol
其它的将与特异的细胞质结合蛋白相结合 others will associate with specialized cytosolic proteins
而被引入线粒体和其它细胞器 and be imported into mitochondria or other organelles
分泌蛋白和膜内在蛋白质的合成同样开始于游离核糖体 The synthesis of cell-secreted and integral membrane proteins is initiated by free ribosomes
随后将停泊在内质网表面的转运蛋白上继续合成 which then dock to protein translocators at the surface of endoplasmic reticulum
新合成的蛋白质将通过一个在转运蛋白上的水合的孔 Nascent proteins pass through an aqueous pore in the translocator
细胞分泌蛋白将在内质网的内腔中聚积 Cell-secreted proteins accumulate in the lumen of endoplasmic reticulum