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Chapter 13 Carbohydrates 1 13.5 Disaccharides Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Important Disaccharides 2 A disaccharide consists of two monosaccharides. Monosaccharides Disaccharide glucose + glucose maltose + H2O glucose + galactose lactose + H2O glucose + fructose sucrose + H2O Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Maltose 3 Maltose is • a disaccharide also known as malt sugar • composed of two D-glucose molecules • obtained from the hydrolysis of starch • used in cereals, candies, and brewing • found in both the and β forms Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Formation of Maltose 4 Maltose is linked by an -1,4-glycosidic bond formed from the OH on carbon 1 of the first glucose and OH on carbon 4 of the second glucose. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Lactose 5 Lactose • is found in milk and milk products • is a disaccharide of β-D-galactose and α- or β-D-glucose • contains a β-1,4-glycosidic bond Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Sucrose 6 Sucrose, or table sugar, • is obtained from sugar cane and sugar beets • consists of α-D-glucose and β-D-fructose • has an α,β-1,2-glycosidic bond Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Sucrose 7 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 8 For the following disaccharide, list the two monosaccharide units and the type of glycosidic bond present. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 9 For the following disaccharide, provide the reaction for two monosaccharide units and the type of glycosidic bond present. galactose + glucose melibiose + H2O The sugar melibiose is formed from two monosaccharides, galactose and glucose, which are joined by a -1,6-glycosidic bond. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Sweetness of Sweeteners 10 Sugars and artificial sweeteners • differ in sweetness • are compared to sucrose (table sugar), which is assigned a value of 100 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Artificial Sweeteners - Sucralose 11 Sucrolose is made from sucrose by replacing some of the hydroxyl groups with chlorine atoms. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Artificial Sweeteners - Aspartame 12 Aspartame is • marketed as Nutra-Sweet • a noncarbohydrate sweetener made from aspartic acid and a methyl ester of the amino acid phenylalanine Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 13 Identify the monosaccharides in each of the following: A. Lactose (1) α-D-Glucose (2) β-D-Fructose (3) β-D-Galactose B. Maltose (1) α-D-Glucose (2) β-D-Fructose (3) β-D-Galactose C. Sucrose (1) α-D-Glucose (2) β-D-Fructose (3) β-D-Galactose Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 14 Identify the monosaccharides in each of the following: A. Lactose (1) α-D-Glucose (3) β-D-Galactose B. Maltose (1) α-D-Glucose C. Sucrose (1) α-D-Glucose (2) β-D-Fructose Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.
