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Cyclic monosaccharides. Cyclic structure. Most of the time, monosaccharides exist as ring structures formed when a carbonyl group and a hydroxyl group in the SAME molecule react This results in a ring structure that is more stable . Drawing a cyclic glucose. Turn the chain on its side
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Cyclic structure • Most of the time, monosaccharides exist as ring structures formed when a carbonyl group and a hydroxyl group in the SAME molecule react • This results in a ring structure that is more stable
Drawing a cyclic glucose • Turn the chain on its side • Fold the chain into a hexagon • Called a Haworth structure • Bond the 1st carbon to a new OH group • If down = alpha / up = beta
Chemical properties of monosaccharides • Oxidation of monosaccharides • The aldehyde group of the open chain structure oxidizes easily • This produces a carboxylic group • Monosaccharides that reduce another group (are oxidized) are called reducing sugars
disaccharides • Easily hydrolyzed into their two monosaccharides • Maltose + water glucose + glucose • Lactose + water glucose + galactose • Sucrose + water glucose + fructose
What links the monosaccharides? • When a hydroxyl group of one monosaccharide reacts with a hydroxyl group of another, a glycosidic bond forms, forming a disaccharide