24-11 Complex Sugars in Nature:Disaccharides f sucrose is related to the mutarotation of 2aa 0hearahedisacehsrndeoa-gucopranoeeand me86h26ee1oea8onee26t2aiooscule ras月8gtucopyanosetothequbrim Acetals link the components of complex sugars. Other acetal linkages be by th 0+ g85io7anmsnoecuesofgucoeyaqueo eet as sugar e the .a f-o-ecepyra Hb-o-ghopyra us hydrolysis yields two molecules of olucose 8 8 24-11 Complex Sugars in Nature: Disaccharides Sucrose is a disaccharide derived from glucose and fructose. Sucrose is a disaccharide composed of glucose and fructose. It is a non-reducing sugar, does not form an osazone and does not undergo mutarotation. The acetal bridge connecting the two simple sugar molecules therefore must connect the two anomeric carbon atoms. Treatment of sucrose with aqueous acid decreases the specific rotation from +66.5o to -20o. The enzyme invertase causes the same decrease. This inversion of sucrose is related to the mutarotation of monosaccharides. •Hydrolysis of the disaccharide to α-D-glucopyranose and β- D-fructofuranose •Mutarotation of α-D-glucopyranose to the equilibrium mixture with the β form •Mutarotation of β-D-fructofuranose to the slightly more stable β-D-fructopyranose The resulting mixture, sometimes called invert sugar, has a net negative rotation, inverted from that of the original sucrose solution. Acetals link the components of complex sugars. Other acetal linkages between monomeric sugars are possible. Maltose is obtained in 80% yield by the action of the enzyme amylase on starch: Maltose is a reducing sugar, forms osazones and undergoes mutarotation. Maltose is hydrolyzed to two molecules of glucose by aqueous acid or by the enzyme maltase. Maltose is 1/3 as sweet as sugar. Cellobiose is identical to maltose with the exception that the anomeric linkage is β instead of α. Aqueous hydrolysis yields two molecules of glucose. A different enzyme, β-glucosidase, is required for enzymic hydrolysis. Maltase is specific for the α-linkage. Lactose, or milk sugar, constitutes more than 1/3 of the solid residue remaining upon evaporation of milk. The linkage between glucose and galactose is β. Crystallization from water furnishes only the α anomer