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