F08-BCH361-L19

F08-BCH361-L19 - Polysaccharides Polysaccharides Starch is...

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Unformatted text preview: Polysaccharides Polysaccharides Starch is used for energy storage in plants a polymers of -D-glucose units amylose amylose : continuous, unbranched chains of up to 4000 -D-glucose units joined by -1,4- glycosidic bonds The monomer of starch ( Amylose) is the -anomer of glucose with an -(1 , 4 linkage), leading to a helical structure Storage of glucose in plants amylopectin amylopectin: a highly branched polymer consisting of 24- 30 units of D-glucose joined by -1,4-glycosidic bonds and branches created by -1,6-glycosidic bonds -1,4-glycosidic bonds -1,6-glycosidic bonds In animals, glucose is stored in the form of glycogen: the main structure is the same but glycogen is more highly branched than Amylopectin starch granules in plants glycogen granules in an animal Plants contain a second polysaccharide which is the major structural component of plants: cellulose cotton and paper are made of cellulose Cellulose: Cellulose: the major structural component of plants, especially wood and plant fibers a linear polymer of approximately 2800 D-glucose units per molecule joined by -1,4-glycosidic bonds fully extended conformation with alternating 180 flips of glucose units extensive intra- and intermolecular hydrogen bonding between chains cellulose fibers Termites and cattle can digest cellulose because of a bacteria they contain in their digestive tracks. The bacteria produce the enzyme cellulase, which can digest the -glycosidic bond Plant Cell Walls consist largely of cellulose also contain pectin, which functions as an intercellular cementing material (pectin is a polymer of D- galacturonic acid joined by -1,4-glycosidic bonds) the major nonpolysaccharide of cell walls, especially in woody plants, is lignin Polysaccharides in insects Chitin: Chitin: the major structural component of the exo-skeletons of invertebrates, such as insects and crustaceans; also occurs in cell walls of algae, fungi, and yeasts composed of units of N-acetyl- -D-glucosamine joined by -1,4- glycosidic bonds CHO CH 2 OH NH-CCH 3 H H HO H HO OH H O N-Acetyl-D-glucosamine (insert bottom of Fig 13.23) The petidoglycan layer stabilizes the cell membrane of procaryotes Bacterial Cell Walls The peptidoglycan of a bacterial cell wall Glycoproteins...
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This note was uploaded on 09/30/2011 for the course BCH 361 taught by Professor Fromme during the Fall '08 term at ASU.

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F08-BCH361-L19 - Polysaccharides Polysaccharides Starch is...

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