E the carbonyl carbon can be oxidized to a carboxylic

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Unformatted text preview: By cyclizaCon, carbonyl C becomes a new chiral center – anomeric carbon •  2 different isomers can be formed – α and β anomers •  Inter ­conversion of the α/β forms occurs through the linear form •  Anomers can have different properCes •  hep://www.biochem.arizona.edu/classes/bioc462/462a/jmol/monosacc/sugar11.htm 36% 64% Sugars can adopt different conformaCons •  Conformation of pyranoses: Rings are not planar •  Bulky substituents occupy equatorial positions rather than the more crowded axial positions equatorial axial β ­D ­Glucopyranose all equatorial posiCons Sugars can be modified Glycosidic bond •  CondensaCon of an alcohol and hemiacetal or hemiketal •  Large diversity possible: –  Different monosaccharide units –  Anomeric carbon can be in α or β conformaCon –  Linkage through different –OH groups Carbohydrates with a free anomeric carbon can act as reducing agents (reducing sugars): i.e. the carbonyl carbon can be oxidized to a carboxylic acid. Common Disaccharides Polysaccharides (Glycans) Branching Structural Polysaccharides •  Cellulose: –  –  –  –  Homopolymer, β1→4 linked glucose unbranched 10,000 ­15,000 glucose units/chain Plant cell walls •  ChiCn: –  Homopolymer, –  β1→4 linked N ­acetylglucosamine –  exoskel...
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This test prep was uploaded on 02/25/2014 for the course BIOC 462A taught by Professor Ziegler,baldwin during the Spring '08 term at University of Arizona- Tucson.

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