General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.1 Chapter 15 Carbohydrates 15.5 Disaccharides

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.2 Important Disaccharides A disaccharide  consists of two monosaccharides Monosaccharides Disaccharide Glucose + glucose maltose + H 2 O Glucose + galactoselactose + H 2 O Glucose + fructosesucrose + H 2 O

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.3 Maltose Maltose is  a disaccharide also known as malt sugar  composed of two D -glucose molecules  obtained from the hydrolysis of starch  linked by an  -1,4-glycosidic bond between the  —OH on C1 of the first glucose and —OH on C4 of the second glucose  used in cereals, candies, and brewing  found in both the  - and  - forms

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.4 Formation of Maltose

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.5 Lactose  is a disaccharide of  - D -galactose and  - or  - D - glucose  contains a  -1,4-glycosidic bond  is found in milk and milk products  is found in both the  - and  - forms

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.6 Lactose (continued)

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.7 Sucrose Sucrose, or table sugar,  is obtained from sugar cane and sugar beets  consists of  - D -glucose and  - D -fructose  has an ,  -1,2-glycosidic bond

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.8 Learning Check Draw the Haworth structures and give the names of the two monosaccharides that form when sucrose is hydrolyzed.

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.9 Solution

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.10 Sweeteners Sugars and artificial sweeteners  differ in sweetness  are compared to sucrose (table sugar), which is assigned a value of 100

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.11 Learning Check Identify the monosaccharides in each of the following: A. lactose 1)  - D -glucose 2)  - D -fructose 3)  - D -galactose B. maltose 1)  - D -glucose 2)  -D-fructose 3)  - D -galactose C. sucrose 1)  - D -glucose 2)  - D -fructose3)  - D -galactose

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.12 Solution Identify the monosaccharides in each of the following: A. lactose 1)  - D -glucose 3)  - D -galactose B. maltose 1)  - D -glucose C. sucrose 1)  - D -glucose 2)  - D -fructose