Chapter 2: The Structure and Function of Macromolecules Polymer Principles POLYMER: large molecule consisting of many identical or similar subunits connected together MONOMER: subunit or building block molecule of a polymer MACROMOLECULE: large organic polymer *Examples: carbohydrates, lipids, proteins, nucleic acids POLYMERIZATION REACTIONS: chemical reactions that link 2 or more small molecules (monomers) to form larger molecules (polymers) DEHYDRATION SYNTHESIS REACTIONS (or CONDENSATION): reactions during which monomers are linked together; an H and and OH are removed, producing net removal of a water molecule for each covalent linkage OHHO O H2OH2O Glucose C 6 H 12 O 6 Fructose C 6 H 12 O 6 Sucrose C 12 H 22 O 11 Water HYDROLYSIS: process that breaks the covalent bonds between monomers by the addition of water molecules *Example: DIGESTION O H2OH2O Sucrose C 12 H 22 O 11 Water OHHO Glucose C 6 H 12 O 6 Fructose C 6 H 12 O 6 Monosaccharides = single sugars are major nutrients for cells glucose is most common *examples: glucose, ribose, galactose, fructose Disaccharides = double sugars Also a source of energy Formed when 2 monosaccharides combine in a dehydration reaction; Examples: lactose (milk sugar): glucose + galactose sucrose (table sugar): glucose + fructose Polysaccharides = hundreds or thousands of monosaccharides formed by linking monomers in DEHYDRATION SYNTHESIS REACTIONS. Disaccharide Examples of energy storage polysaccharides: starch = glucose polymer in plants used for energy storage (in roots, tubers, etc.) glycogen = glucose polymer in animals stored in skeletal muscles and liver of humans & other vertebrates Examples of structural support polysaccharides: cellulose = structural component of plant cell walls that cannot be digested by most organisms chitin = forms exoskeletons of arthropods LIPIDS insoluble in water (because they are NONPOLAR, or HYDROPHOBIC) include: 1.Fats 2.Phospholipids 3.Steroids 1. FATS Composed of: A large proportion of C-H bonds and less oxygen than carbohydrates (the nonpolar C-H bonds make the chain hydrophobic and insoluble in water) Example: C 57 H 110 O 6 during formation of a fat, dehydration synthesis reactions link fatty acids to glycerol Fatty acids may vary in # of carbon atoms (usually even #) Saturated vs. Unsaturated Fats SATURATED FATUNSATURATED FAT no C-C double bonds in fatty acid tail usually solid at room temp. most animal fats e.g., bacon grease, lard, butter one or more C-C double bonds in fatty acid tail usually a liquid at room temp. most plant fats e.g., corn, peanut, olive oils Functions of Fats energy storage (1 g of fat stores 2x as much energy as 1 g of carbohydrate) cushions vital organs in mammals (e.g. kidney) insulates against heat loss (e.g. whales, seals) 2. PHOSPHOLIPIDS Important component of cell membranes 3. STEROIDS Important component of some hormones Cholesterol is used to make many other steroids (including sex hormones in vertebrates) common component of cell membranes can cause atherosclerosis (if have too much)