Lecture 13 - ribose, fructose to glucose) Glycosidic bonds:...

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Lecture 13 Carbohydrates (and their relatives) C n (H 2 O) n 1. metabolic intermediates (C, energy sources: glucose, glyceraldehyde) 2. storage forms (poly-glucose: starch, glycogen) 3. structural materials (cellulose, callose, chitin; also algin, agar, carageenan) 4. indicators, antigens, etc. for cell recognition (glycolipids, glycoproteins, proteoglycans) Stereochemistry provides variety (Fig. 7.2) (note “aldoses” “chiral center”; L-forms: mirror images of D forms at all C’s)
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Cyclization (Fig. 7.5) (note “pyranose” ring, anomeric C) evidence that linear form exists in solution: there is always a mixture of a, ß forms; there is oxidation of the C1 aldehyde to acid (“reducing sugar”) similar cyclization with a sugar acid:
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(note “ketoses” Fig. 7.3: ribulose, fructose; “furanose” ring, Fig. 7.6; compare ribulose to
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Unformatted text preview: ribose, fructose to glucose) Glycosidic bonds: oligo- and polysaccharides Disaccharides (Fig. 7.18) Maltose: glucose- 1,4-glucose Lactose: galactose- 1,4-glucose Sucrose: glucose-1 , 2-fructose (non-reducing) Trehalose: glucose- 1,1-glucose (non-reducing) (cf. p. 193) Polysaccharides Amylose and amylopectin (Figs. 7.20, 7.21) amylose: glucose- 1,4-glucose n (note helical form) amylopectin: amylose with glucose- 1,6-glucose branches Cellulose (Fig. 7.26) glucose- 1,4-glucose (note straight form) Chitin: N-acetyl-glucosamine- 1,4-N-acetyl-glucosamine (like cellulose) :N-acetyl-glucosamine- chains also found in proteoglycans Problems: Ch. 7, p. 216: 4,6,8...
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Lecture 13 - ribose, fructose to glucose) Glycosidic bonds:...

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