1. Biological Macromolecules • Large molecules that perform many important biological functions • Carbohydrates • Lipids • Proteins • Nucleic Acids • Many are polymers • Large molecule that is made of repeating units of identical or similar subunits • Each subunit=monomer

2. Biological Polymerization • Accomplished through covalent bonding • Often takes place via dehydration reactions which result in the release of a water molecule/bond formed • Process can be reversed by hydrolysis which breaks bonds by the addition of water

3. Fig. 5-2 HO HO H 1 2 3 H Short polymer Unlinked monomer Dehydration removes a water molecule, forming a new bond H2O HO 2 H 4 1 3 Longer polymer (a) Dehydration reaction in the synthesis of a polymer HO H 3 4 2 1 Hydrolysis adds a water molecule, breaking a bond H2O H HO HO 2 H 1 3 (b) Hydrolysis of a polymer

4. Carbohydrates • Comprises sugars and polymers of sugars • Used for variety of functions • Energy-simple sugars • Storage of energy-starches • Structural components-cellulose and chitin

5. Monosaccharides • Simple sugars=monomers • Usually have chemical composition of CxH2xOx • Can exist as chains or rings (usually rings in solution) • Monosaccharides combine to form disaccharides

6. Sugar Classification • Sugars may be classified by: • Number of carbons in chain • Location of carbonyl group • Position of side groups from asymmetrical carbon

7. Fig. 5-3 Trioses (C3H6O3) Pentoses (C5H10O5) Hexoses (C6H12O6) Aldoses Glyceraldehyde Ribose Glucose Galactose Ketoses Dihydroxyacetone Ribulose Fructose

8. Disaccharide Formation • Disaccharides are formed by the dehydration reaction between two monosaccharides • Bond between monosaccharides is called the glycosidic linkage • Linkage may occur between different different carbons

9. Fig. 5-5 1–4 glycosidic linkage Glucose Glucose Maltose (a) Dehydration reaction in the synthesis of maltose 1–2 glycosidic linkage Glucose Fructose Sucrose (b) Dehydration reaction in the synthesis of sucrose

10. Storage Carbohydrates • Polysaccharides=many monomers in one polymer • Glucose is most common monomer used • Starches =plants use for energy storage • Amylose is unbranched chain of glucose monomers • Glycogen=animals use glycogen as medium-term energy storage • Glycogen is highly-branched polymer of glucose monomers • Cells contain enough glycogen for approximately one day’s activity

11. Structural Carbohydrates • Cellulose • Most abundant organic compound on earth • Plants use cellulose as structural component of cell walls • Most animals cannot digest • Certain bacteria can degrade cellulose • Cows and termites have symbiotic relationship w/ bacteria • Fiber in your diet usually means cellulose • Not digested so acts as a mechanical cleansing mechanism as it passes through the intestines • Comprises polymerized units of glucose

12. Starch vs Cellulose • Both use 1-4 glycosidic linkage of glucose • Starch uses a configuration of glucose • Results in helical molecule • Cellulose uses B configuration of glucose • Forms linear strands that interact to form fiber bundles

13. Structural Carbohydrates 2 • Chitin • Comprises polymer of N-acetylglucosamine (NAG) • Similar to glucose but possesses a nitrogen-containing side chain • Major component of insect and crustacean exoskeleton • Major component of fungal cell walls • Can be flexible or made rigid by interacting with calcium • Cross-links the structure

14. Carbohydrate Summary • Can be used for energy, storage and structural uses • Designated by length of carbon chain, location of carbonyl group, and position of side groups around asymmetric carbons • Glucose and modified glucose is used in all three major functions of carbohydrates