1 chapter 16 carbohydrates 16.7 disaccharides 16.8 polysaccharides

10
1 Chapter 16 Carbohydrates 16.7 Disaccharides 16.8 Polysaccharides

Post on 21-Dec-2015

221 views

Category:

Documents


0 download

TRANSCRIPT

1

Chapter 16 Carbohydrates

16.7 Disaccharides

16.8 Polysaccharides

2

Disaccharides

A disaccharide consists of two monosaccharides.

Disaccharide Monosaccharides Maltose + H2O Glucose + Glucose

Lactose + H2O Glucose + Galactose

Sucrose + H2O Glucose + Fructose

3

Maltose

Maltose is: A disaccharide in

which two D-glucose molecules are joined by an -1,4-glycosidic bond.

Obtained from starch.

Used in cereals, candies, and brewing.

4

Lactose

Lactose is: Also called milk

sugar. Composed of

galactose and glucose linked by a -1,4-glycosidic bond.

5

Sucrose

Sucrose: Is the disaccharide

known as table sugar. Is composed of glucose

and fructose molecules joined by ,-1,2-glycosidic bond.

Has no isomers because mutarotation is blocked.

6

Sweetness of Sweeteners

Sugars and artificial sweeteners differ in sweetness.

Each sweetener is compared to sucrose (table sugar), which is assigned a value of 100.

7

Polysaccharides Polysaccharides are

polymers of D-glucose Important polysaccharides

are:

Starch (Amylose and

Amylopectin)

Glycogen

Cellulose

O

OH

CH2OH

OH

OH

OH

D-Glucose

8

Amylose, Amylopectin, and Glycogen

Amylose is a continuous chain of glucose molecules linked by -1,4 glycosidic bonds.

Amylopectin is a branched chain of glucose molecules linked by -1,4- and -1,6-glycosidic bonds.

Glycogen is similar to amylopectin, but more highly branched.

9

Structures of Amylose and Amylopectin

10

Cellulose Cellulose is a polymer of glucose molecules

linked by -1,4 glycosidic bonds. Enzymes in saliva can hydrolyze -1,4

glycosidic bonds in starch, but not -1,4 glycosidic bonds in cellulose.