Carbohydrates Section 3.2

Learning Objectives Explain the difference between monosaccharides, disaccharides, & polysaccharides Give examples of monosaccharides, disaccharides, & polysaccharides Compare storage polysaccharides with structural polysaccharides

Carbohydrate Basics Carbohydrate = Compound made up of C, H, & O in the ratio of 1C:2H:1O Example: C6H12O6 Names usually end in -ose Monomer units are monosaccharides (simple sugars) Examples: glucose, fructose, & galactose Glucose is the most abundant Main function is to serve as an energy source

(Don’t copy!) Glucose and Fructose are Structural Isomers! Aldehyde – C=O bond is on an end carbon atom Ketone – C=O bond is on an interior carbon atom

Monosaccharides in Solution Many monosaccharides form rings in aqueous solution (water) Ring diagrams may be abbreviated by not showing the carbons at the corners

Disaccharides Disaccharides = 2 monosaccharides connected by a glycosidic linkage Monomers joined by a condensation reaction Are a nutritional source of monosaccharides Examples: sucrose, lactose, & maltose Glucose ➞ ← Fructose Sucrose

Polysaccharides Polysaccharides —long chains of simple sugars Function is energy storage and structural support Examples include: Starch —glucose storage in plants Glycogen —glucose storage in animals Cellulose —tough fibers that give plants strength and rigidity Chitin – tough polymer found in cell walls of fungi (mushrooms) & exoskeletons of arthropods (ex. crustaceans & insects)

Digesting Cellulose Animals do not have an enzyme that can break down cellulose Can’t hydrolyze cellulose There are some bacteria species that can digest cellulose Live in the digestive system of termites, cows, and sheep

Other Carbohydrates Glycoproteins = carbohydrate bonded to a protein Found in the cell membrane of cells Allow cells to stick to each other or provides protection Glycolipids = carbohydrate bonded to a lipid molecule Allow cells to recognize & interact with each other