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1、Plant cell and its wall 毛自朝 Outline of this charptor Membrane structure Membrane organelles Cell wall and its architecture Structure of membrane The fluid-mosaic model This model emphasis the mosaic（镶嵌）: 流动的酯双分子层中镶嵌着流动的蛋白 Fluid（流动性）：脂质是液晶态随温度变 化而流动 （asymmetric) 对称性:different distribution of lipids a
2、nd proteins Plasma membrane Lipid composition is highly variable Protein serve as variety function Electrochemical gradient produced by H+- ATPase driving many transport systems Several class of membrane mediate interaction with cell wall and receptor has been indentified Interaction of endo-menbran
3、e system Golgi Apparatus TGN unit consist of morphologically distinct cisternae give rise to different type of coated vesicle Serve as carbohydrate factory Xyloglucan Pectic polysaccharidesVacuoles Cheaply produce large cell Multiple function including storage Digestion ,pH and ionic homeostasis, mi
4、crobial defense ,sequestration of toxic compounds and pigmentation The nucleus and its nuclear pore complex Peroxisomes Mitochondrion Resemble prokaryotes Like all plastids ,are semiautonomous ,posses the genetic machinery to make some of its protein Cell power supplied station Plastid and Chloropla
5、st Thylakoid Stacked grana Interconnection stroma Why cell wall important (Chemically )Composed of polysaccharides ,proteins and aromatic substances (Structurally): middle lamella ,primary wall second wall Polysaccharide :Cellulose micro fibrils (scaffold), Hemicelluloses cross link the Cellulose mi
6、cro fibrils ,and the cellulose and hemicelluloses complex is embedded by pectin gel Cell wall is borne at cell plate and cell enlargement dependent on combination activities of endglycosidase ,endotransglycosidse ,and expansin Constitute major dietary fibers for human nutrition, used in wood paper a
7、nd textile product ,biomass for bio- energy and bio-chemicals . Macromolecules of cell wall Cellulose ,principle scaffolding component Cellulose scaffolding is interlocked by other glycan (hemicelluloses) Pectin matrix (rich galacturonic polymers )are fill between cell wall Structural protein are en
8、coded by large gene familliesHemicelluloses Two major flower plant : Xyloglucan (XyGs) Cross link the wall of dicots and one half of momocots Glucurono-arabino-xylan(GAXs) commelinoid (鸭跖草族)including bromeliads(凤 梨科), palm (棕榈科)，gingers (姜科）Cypress （莎草科）and grasses(禾本种 )XyGs Liner chain of 1-4 b-D-g
9、lucan Regularly o-6-glu unit was substituted with numerous a-D-Xyl Some of a-D-Xyl was further substituted by b-D-gal or a-L-Ara sometimes b-D-gal or a-L-Ara was further substituted by a-L-fuc. GAX Glucurono-arabino-xylan All angiosperms contain at least small amounts of GAXs As major cross lonk pol
10、ymer In commelinoid monocotsOther link polymer Mix linkage (1-3),(1-4)b Glucan Glucomannans Galactoglucomannans Galactomannans Pectin matrix Highly hydrated polysaccharides rich in D-galacturonic acid ,two fundamental constitutent areHGA (home galacturonan )and RGI (rhamno galacturonan I),and their
11、mofified form xylogalacturonan and rhamno galacturonanII(RGII) Dertermining wall porosity Providing charged suefaces that modulate pH and ion balance Regulating cell to cell adhesion Alert plant cell to presence of symbiotic organism ,pathogen and insects Structural protein of cell wall HRGPs (hydro
12、xy-proline rich glycoprotein ) PRPs(proline rich proteins) GRPs(glycine rich proteins) Arabinogalactan protein Aromatic substance Large fraction was hydroxyl-cinnamic acid (ferulic acid and coumaric acid)Cell wall architecture Building block is coming from many way ,so does the architecture Primary
13、cell is made of two, some times three structurally independent but interaction networkWall of angiosperms are arranged in two different architecture Type I cell wall Most dicots and non-commelinoid contain nearly equal amounts of XyGx and cellulose .with average 200 nm XyGx are enough to bind two ce
14、lllose microfibrilis. And XyGx , cellose network are embedded in pectin matrix two pectin layers are connected by salts bond of Ca2+ Type II cell wall 1.Commelinoid momocots cell wall2.Similar with type I , instead of XyGx, GAX is the principle polymers to interlock the cellulose micro-fibrils 3.pec
15、in is less than typeI but GlA in GAX providing salts bond with Ca2+4.less structural protein by comparison with typeI ,but the accumulated extensive interconnection of phenylpropanoids Cell wall biosynthesis and assembly Originated from the developing cell plates During the telophase of mitotic cell ,a phragmosome, was form by a flatten membrane vesicles contain cell wall components was arranged by cell cytoskeleton. ,except cellulose , polysaccharides, structural protein, and a broad spectrum cell synthesis enzyme were secreted by Golgi apparatus derived vesicles Polys
