1. Chapter 14
14.6 – Polysaccharides

2. Polysaccharides A polymer of many monosaccharides joined together
Four biologically important polysaccharides:
Amylose
Amylopectin
Glycogen
Cellulose
All are polymers of D-glucose that differ only in the type of glycosidic bonds and the amount of branching in the molecule

3. Starch Starch is a storage form of glucose in plants
Found as insoluble granules is rice, wheat, potatoes, beans and cereals
Starch is composed of two kinds of polysaccharides – amylose and amylopectin

4. Amylose Amylose – makes up about 20% of starch
Contains 250 to 4000 α-D-glucose molecules connected by
α-1,4-glycosidic
bonds in a
continuous chain
They are actually
coiled in a helical
fashion

5. Amylopectin Amylopectin – makes up about 80% of starch
Glucose molecules are connected by
α-1,4-glycosidic
bonds in a
branched chain
About every 25
glucose units
there is an
α-1,6-glycosidic
bond

6. Glycogen
Animal starch that is a polymer of glucose that is stored in the liver & muscle of animals
Hydrolyzed in our cells at a rate that provides energy between meals
Structure is similar to amylopectin but it is more highly branched
Glucose units are joined by
α-1,4-glycosidic bonds with
branches occurring about
every glucose units
attached by α-1,6-glycosidic bonds

7. Cellulose Is a polysaccharide of glucose units in unbranched chains
Has β-1,4-glycosidic bonds – do not form coils like the α isomers but are aligned in parallel rows (insoluble in water)
Cannot be digested by humans - we cannot break down β-1,4-glycosidic bonds

8. Cellulose
Cotton is almost pure cellulose

9. Carbohydrates in Our Diet