07 - CHAPTER 7 Carbohydrates Biochemistry: The Molecular...

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Biochemistry: The Molecular Basis of Life, 4/e McKee/McKee Copyright © 2009 by Oxford University Press, Inc. C H A P T E R 7 Carbohydrates
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Overview Carbohydrate = [CH 2 O] n Most abundant organic molecule class – photosynthesis. Functions: - energy http://www.youtube.com/watch?v=jJvAL-iiLnQ&feature=related - structural elements - precursors - cell-cell communication - cell identity - information system (sugar code) - glycoconjugates Mono-, di-, oligo- & poly- Monosaccharides (simple sugars) = polyhydroxy aldehydes (aldoses) or ketones (ketoses). Triose, tetrose, pentose, hexose , heptose, . .. The smallest sugars: glyceraldehyde & dihydroxyacetone . Fischer projection: vertical C-backbone; most oxidized C at the top. 7.1 Monosaccharides FIGURE 7.2 Glyceraldehyde (an Aldotriose) and Dihydroxyacetone (a Ketotriose)
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Monosaccharide stereoisomers Multiple chiral C atoms; n chiral atoms ! 2 n stereoisomers. D- (most natural sugars) & L- stereoisomers – based on the C that is most remote from C=O. D- is based on D-glyceraldehyde. Diastereomers = stereoisomers that are not enantiomers. Epimers = diastereomers that differ by 1 assymetrical C. FIGURE 7.3 The D- Family of Aldoses FIGURE 7.4 The Optical Isomers D- and L-Ribose and D- and L-Arabinose
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FIGURE 7.5 Formation of Hemiacetals and Hemiketals Cyclic structure of monosaccharides Cyclic form (hemiacetal or hemiketal) most stable. Cyclization ! new chiral C (anomeric): 2 anomers. For D sugars: α -anomer : ‘new’ OH - down β -anomer: ‘new’ OH - up. Haworth structures Pentose = furanose, hexose = pyranose. FIGURE 7.6 Monosaccharide Structure FIGURE 7.7 Haworth Structures of the Anomers of D-Glucose FIGURE 7.8 Furan and Pyran
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Conformational structures Most realistic. FIGURE 7.9 Fischer and Haworth Representations of D-Fructose FIGURE 7.10 α - and β -D-Glucose
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FIGURE 7.11 Equilibrium Mixture of D-Glucose Mutarotation = spontaneous interconversion of α & β forms in water.
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FIGURE 7.12 Oxidation Products of Glucose
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This note was uploaded on 10/15/2010 for the course MOLB 3610 taught by Professor Gomelsky during the Fall '10 term at Univeristy of Wyoming- Laramie.

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07 - CHAPTER 7 Carbohydrates Biochemistry: The Molecular...

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