Extracellular_interactions

Extracellular_interactions - - majority of info is on...

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Topic 4 – Extracellular interactions Reading Chapter 28.1a, 32.2 On-line sources (read selectively) Objectives BIO 1140 – SLIDE 1 Plant cell walls and plasmodesmata Animal cells The social network The extracellular matrix Marchiando et al, 2010 J Cel Biol 189, 111-126 Plant cell walls and plasmodesmata Provides rigidity and protection, regulates permeability Structure involves 3 classes of molecules Structural fibres – cellulose microfibrils Matrix – polysaccharides (e.g. hemicellulose, pectins) Adhesive molecules – pectins BIO 1140 – SLIDE 2 Fig. 28.3 Plasma membrane Cel wal Middle lamel a Plant cell walls and plasmodesmata Provides rigidity and protection, regulates permeability Structure involves 3 classes of molecules Structural fibres – cellulose cellulose microfibrils microfibrils Matrix – polysaccharides (e.g. hemicellulose, pectins) Adhesive molecules – pectins BIO 1140 – SLIDE 3 Purple pages , F23 - majority of info is on online resources - multicellular organisms have issue - the cells in these organisms are formed into tissues - must be able to bond to each other and recognize each other - plants and fungi - cell wall - protection and rigidity to the cell and limits the cell to cell connections that can occur - animal cells - lot more ways to connect cells - plant cell wall and animal cytoskeleton - very similar -- plant cell wall - matrix - some glycoproteins called extensins thrown in, but primarily polysaccharides --- matrix - sticky mass - polysaccharides have mostly negative charge - attracts water --- main part of the matrix is made up of hemicellulose - quite extensive side chains - pectin - found in jam - backbone carries strong negative charge - attraction to water - produces jell like consistency - cellulose- repeated units of beta glucose - beta glycosidic bonds - forms rigid, linear structure - cellulose microfibrils are embedded in the matrix to provide rigidity and strength --- not synthesized in the cell - on surface of the cell membrane - enzymes that are transmembrane proteins that move around in the plasma membrane to synthesize cellulose - enzyme rosettes - move around in the plasma membrane - driven by motor proteins and cell controls the pattern of the cellulose by how the rosettes move around in the plasma membrane on microtubules
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Plant cell walls and plasmodesmata Provides rigidity and protection, regulates permeability Structure involves 3 classes of molecules Structural fibres – cellulose cellulose microfibrils microfibrils Matrix – polysaccharides (e.g. hemicellulose, pectins) Adhesive molecules – pectins BIO 1140 – SLIDE 4 Fig. 17-24, Becker et al. 2009 rosettes Primary vs secondary cell wall Middle lamella (pectins) Primary cell wall – loose network of cellulose fibrils Secondary cell wall – cellulose fibrils highly organized Multi-layered Lignin cytoplasm 1° wal 2° wal Middle lamel a
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This note was uploaded on 03/26/2012 for the course BIO 1140 taught by Professor Fenwick during the Winter '07 term at University of Ottawa.

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Extracellular_interactions - - majority of info is on...

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