chapter04生物学.pptVIP

Chapter 4 Interactions Between Cells and Their Environment OUTLINE 4.1 CELL SURFACE 4.2 CELL ENVIRONMENT 4.3 CELL RECOGNIZATION 4.4 CELL JUNCTION 4.1 Cell Surface Structure： ●cell coat ● Plasma membrane ●cortical cytosol membrane cytoskeleton ◆Glycocalyx ●the composition of glycocalyx： 由细胞表面的碳水化合物形成的质膜保护层，又称为多糖包被。 ● Function ： The glycocalyx is thought to mediate cell-cell and cell-substratum interactions, provide mechanical protection to cells, and serve as a barrier to particles moving toward the plasma membrane. 4.1.2 Plant Cell Walls ◆formation of middle lamella 首先合成 ◆formation of primary cell wall 是细胞正在生长时形成的。初生壁的厚度为100-200nm,与动物细胞的基膜相当。 4.2 Extracellular matrix ●proteoglycan，PG 蛋白聚糖 ●structure protein 结构蛋白 如胶原和弹性蛋白，它们赋予基质一定的强度和韧性。 ● adhesive proteins 黏着蛋白 如纤连蛋白和层粘蛋白，它们促使细胞同基质结合。 4.2.2 Proteoglycan and hyaluronic acid （1 ）Proteoglycan,PG （蛋白聚糖） ◆Structure and Function ● Protein-polysaccharide complex is called a proteoglycan ●A proteoglycan consists of a core protein molecule to which chains of glycosaminoglycans （GAGs,糖胺聚糖） are covalently attached. ●Because of the negative charges borne on the sulfated GAGs, proteoglycans bind huge numbers of cations, which in turn bind large numbers of water molecules. As a result, proteoglycans form a porous, hydrated gel that fills the extracellular space like packing material and resists crushing (compression) forces. （2） Glycosaminoglycans （糖胺聚糖, 粘多糖） ● Each glycosaminoglycan chain is composed of a repeating disaccharide; that is, it has the structure -A-B-A-B-A-, where A and B represent two different sugars. ● GAGs are highly acidic due to the presence of both sulfate and carboxyl groups attached to the sugar rings. ●糖胺聚糖的二糖单位之一是氨基己糖(氨基葡萄糖或氨基半乳糖), 故称为糖胺聚糖。 ●糖胺聚糖包括∶ 硫酸软骨素（chondroitin sulfate） 透明质酸（hyaluronic acid）等。 （3） hyaluronic acid（透明质酸） 细胞外基质中发现的大多数糖胺聚糖，都是作为蛋白聚糖的一个成分而存在，惟一例外的是透明质酸，它在细胞外基质中也可游离存在。 透明质酸在结缔组织中起强化、弹性和润滑作用,具有抗压能力。 A Proteoglycan Complex 4.2.3 Collagen