3. Carbohydrates (CHO) -carbohydrates contain only Carbon, Hydrogen and Oxygen -carbohydrates are produced in the process of photosynthesis

4. Carbohydrates and Energy -main energy source for living things -energy is stored for short term or long term -CHO include sugars, starches, cellulose and chitin -energy stored in chemical bonds that hold carbohydrates together -this energy is then used in any activity that the organism does

5. The Structure of Carbohydrates Remember, all macromolecules are composed of monomers that join together in a deydration synthesis reaction to from polymers. Carbohydrates Monomer(s)Polymers Monosaccharides Polysaccharides Disaccharides Starch Cellulose Chitin Glycogen

6. Types of CHO: -CHO are classified based on the number of simple sugars that they contain and there are three types of carbohydrates according to complexity Monosaccharides -sweet tasting, simple sugars -have 6 carbon atoms and some hydroxyl groups -soluble in water (they dissolve in water) -the three most common monosaccharides are: a)Glucose (main sugar) b) Galactose (sugar found in milk) c) Fructose (sugar found in fruits)

7. Disaccharides/Double Sugars -consist of two monosaccharides linked together (a dehydration synthesis reaction links them together) -the hydroxyl (OH) group of glucose reacts with the hydroxyl (OH) group of fructose -soluble in water (they dissolve in water) http://www.biotopics.co.uk/as/disaccharideformation.html -good animation of a condensation reaction

8. Polysaccharides (Many Sugars)(three or more monosaccharides) -macromolecules that are polymers of a few hundred/thousand monosaccharides -NOT soluble in water (do not dissolve in water) -have two important biological functions 1. Energy Storage (Starch and Glycogen) 2. Structural Support (Cellulose and Chitin) Glycogen -animals store glucose in the form of glycogen in the liver and muscles to be used as quick energy -consists of hundreds of glucose molecules strung together in a highly branched chain - Starch -plants store energy in the form of starch -found in rice, wheat, potatoes, flour, -too large to be absorbed by our digestive system- we have to break them down into monosaccharides

9. Cellulose -a large polysaccharide found in the cell walls of plants -provides structure, protection, rigidity and support -makes up about 50% of wood *humans do not have the bacteria necessary to digest cellulose, therefore it is not a direct energy source for us, that is why we can’t eat hay -makes up wood and paper -we don’t digest it so it goes through us undigested, but it does attract water, and mucus and helps to prevent constipation. Fibre is healthy! Chitin -makes up the exoskeleton of insects and crustaceans -tough material, we don’t digest it well -used to make contact lenses and stitches!