Objectives:1. Identify examples2. Identify formulas3. How are they put together or broken down?4. Basic facts

- Quick, short-term energy.- Always have a 2:1 ratio of hydrogen to oxygen atoms.

–Play a structural role when joined with other molecules.

–C, H, O

Examples :

•Sugars•Starches•Cellulose

Simple Sugars:

• The simplest sugars are made of ONE molecule. They are called:

Fig. 5-3

Dihydroxyacetone

Ribulose

Ket

ose

sA

ldo

ses

Fructose

Glyceraldehyde

Ribose

Glucose Galactose

Hexoses (C6H12O6)Pentoses (C5H10O5)Trioses (C3H6O3)

Monosaccharides...

• These sugars have the same chemical formula, but different structural formulas…therefore they are

Two Monosaccharides...• Two monosaccharides can join together to form a new sugar. This is now called a

Forming disaccharides...• Notice, when forming a disaccharide, what molecule is formed once the sugars join?

• Long term energy storage and structural purposes

• Consist of many glucose molecules linked together.

• The structure and function of a polysaccharide are determined by its sugar monomers and the positions of glycosidic linkages

• Only difference is the pattern:– Starch– Glycogen– Cellulose

• Starch, a storage polysaccharide of plants, consists entirely of glucose monomers

• Plants store surplus starch as granules within chloroplasts and other plastids

• Glycogen is a storage polysaccharide in animals

• Humans and other vertebrates store glycogen mainly in liver and muscle cells

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Fig. 5-6

(b) Glycogen: an animal polysaccharide

Starch

GlycogenAmylose

Chloroplast

(a) Starch: a plant polysaccharide

Amylopectin

Mitochondria Glycogen granules

0.5 µm

1 µm

• The polysaccharide cellulose is a major component of the tough wall of plant cells

• Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ

• The difference is based on two ring forms for glucose: alpha (a) and beta (b)

b Glucosemonomer

Cellulosemolecules

Microfibril

Cellulosemicrofibrilsin a plantcell wall

0.5 µm

10 µm

Cell walls

• Enzymes that digest starch by hydrolyzing a linkages can’t hydrolyze b linkages in cellulose

• Cellulose in human food passes through the digestive tract as insoluble fiber

• Some microbes use enzymes to digest cellulose

• Many herbivores, from cows to termites, have symbiotic relationships with these microbes

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Fig. 5-9

• Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods

• Chitin also provides structural support for the cell walls of many fungi

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The structureof the chitinmonomer.

(a) (b) (c)Chitin forms theexoskeleton ofarthropods.

Chitin is used to makea strong and flexiblesurgical thread.

HOMEWORK:• Assignment # 11 & 12 from your packet

cover, reading and worksheets.