1. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. 13.2 Fischer Projections of Monosaccharides 1 Chapter 13 Carbohydrates

2. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Fischer Projections A Fischer projection is used to represent carbohydrates places the most oxidized group at the top shows chiral carbons as the intersection of vertical and horizontal lines 2

3. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. D and L Notations In a Fischer projection, the  OH group on the chiral carbon farthest from the carbonyl group determines an L or D isomer. left is assigned the letter L for the L form right is assigned the letter D for the D form 3

4. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Examples of D and L Isomers of Monosaccharides 4

5. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Identify each as the D or L isomer. A.B. C. __-Ribose __-Threose __-Fructose 5

6. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution Identify each as the D or L isomer. A.B. C. L-Ribose L-Threose D-Fructose 6

7. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Glucose and Fructose D-glucose is found in fruits, corn syrup, and honey an aldohexose with the formula C 6 H 12 O 6 known as dextrose and blood sugar in the body D-fructose is obtained from lactose an aldohexose with the formula C 6 H 12 O 6 important in cell membranes of the brain and nerve cells 7

8. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Glucose and Fructose The sweet taste of honey comes from the monosaccharides D-glucose and D-fructose. 8

9. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Blood Glucose Level In the body, glucose has a normal blood level of 70–90 mg/dL a glucose tolerance test measures blood glucose for several hours after ingesting glucose 9

10. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. D-Galactose is an aldohexose, C 6 H 12 O 6 is not found free in nature is obtained from lactose, a disaccharide has a similar structure to glucose except for the  OH on carbon 4 In a condition called galactosemia, an enzyme needed to convert galactose to glucose is missing. 10

11. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Learning Check Draw the structure of D-fructose. 11

12. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc. Solution 12