1. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Chapter 13 Carbohydrates 13.5 Disaccharides 1

2. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Important Disaccharides A disaccharide consists of two monosaccharides. Monosaccharides Disaccharide glucose + glucose maltose + H 2 O glucose + galactose lactose + H 2 O glucose + fructosesucrose + H 2 O 2

3. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Maltose 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 3

4. 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.

5. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. 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 5

6. 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

7. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Sucrose 7

8. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check For the following disaccharide, list the two monosaccharide units and the type of glycosidic bond present. 8

9. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution For the following disaccharide, provide the reaction for two monosaccharide units and the type of glycosidic bond present. galactose + glucose melibiose + H 2 O The sugar melibiose is formed from two monosaccharides, galactose and glucose, which are joined by a  -1,6-glycosidic bond. 9

10. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Sweetness of Sweeteners Sugars and artificial sweeteners differ in sweetness are compared to sucrose (table sugar), which is assigned a value of 100 10

11. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Artificial Sweeteners - Sucralose Sucrolose is made from sucrose by replacing some of the hydroxyl groups with chlorine atoms. 11

12. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Artificial Sweeteners - Aspartame Aspartame is marketed as Nutra-Sweet a noncarbohydrate sweetener made from aspartic acid and a methyl ester of the amino acid phenylalanine 12

13. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check 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 13

14. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 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 14