369Lecture12_F11(1)

369Lecture12_F11(1) - + Lecture 11: Ch 11 Carbohydrates...

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Unformatted text preview: + Lecture 11: Ch 11 Carbohydrates CH369 Fall 2011 1 + Reactions of Aldehydes & Ketones 1 acetal group 1 ketal group 2 acetal groups 2 ketal groups 2 + Fischer projection Haworth projections Anomeric C is an alcohol Cyclization of Sugars n Monosaccharide can bite its own tail n C1 is anomeric carbon n C1 condenses w/ O5 to form intramolecular hemiacetal n Right on Fischer = Down on Haworth n α = down (right on Fischer) n β = up (left on Fischer) n Equilibrium between closed and open forms makes anomeric C reactive 3 + Mutarotation: Interconversion of α- and β- anomers Fischer projection Chain form Glucose anomers (aqueous solution) 36% 64% 4 + Reducing Sugars n Reducing sugars are carbohydrates that can reduce oxidizing agents n Carry reactive carbonyl group n Sugars which form open chain structures with free carbonyl group n Reduction of metal ions n Benedict’s reagent: CuSO 4 in alkaline solution 5 + Sugar Derivitization n Reaction of glucose with methanol yields addition of methoxy group to anomeric carbon n No longer reactive n Now a non-reducing sugar n Group linked to anomeric C forms glycosidic bond n Glycoside is sugar linked to another molecule 6 + Sugar Derivitization n Sugars can also be phosphorylated n Gly-3-P n F-6-P n Important intermediates in metabolic pathways n Hydroxyl group can be replaced with amino group n Glucosamine n Oxidation of sugar gives uronic acids n Reduction gives sugar alcohol n Ribose converted to deoxyribose 7 + Polysaccharides 8 n Chains or polymers of carbohydrates n Formed by glycosidic bonds n Aka glycan chains n Can be used to modify other molecules, e.g. glycoproteins or glycolipids n Polysaccharides a common fuel-storage molecules n Can be joined in a variety of ways n Tremendous repertoire of complex molecules! n Multiple –OH groups with different bonding arrangements makes this possible n Need way to classify and understand them that includes this level of complexity n Glycomics n Study of carbs http://faculty.washington.edu/dratner/Research.html + Which of these is a nonreducing sugar? 9 A. (a) B.(b) + Common Disaccharides n Disaccharides occur in nature most commonly as breakdown products of polysaccharides n Lactose n Secreted in milk of lactating mammals n Galactose- Ќ-1,4-glucose n Galactose and glucose, joined by glycosidic bond between #1 C of galactose and the #4 C of glucose n If different C’s were joined to form the bond – we’d have a different disaccharide n Most adult mammals (including humans) produce very little lactase ( Ќ-galactosidase) and have some difficulty in digesting this sugar 10 + Structural Carbohydrates n Cellulose n Glucose polymer formed between #1 and #4 C atoms – like amylose n Linkages are Ќ n Makes for very profound differences in structure n Instead of compact granules (storage form), form extended fibers n Provides rigidity and strength for plant cell walls n Extensive H-bonding network within and between adjacent chains 11 n Animals don’t make it and most cannot digest it n Microbes do n Normal microflora for ruminants Celluose fibers +...
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This note was uploaded on 11/12/2011 for the course CH 369 taught by Professor Kbrowning during the Fall '07 term at University of Texas.

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369Lecture12_F11(1) - + Lecture 11: Ch 11 Carbohydrates...

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