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The Structure and Function of Macromolecules: Four Classes of Organic Molecules AP Biology Chapter 5 Biomolecule - Project You are to become an expert in an assigned biomolecule Organize the main structure and functions of your biomolecule Models are good Note examples & interesting facts… Use visual of transparency / doc camera, poster OR Power point Presentations - Tuesday Polymers and Macromolecules: Polymer: most macromolecules are polymers…a single unit repeated many times, hence “poly”mer Monomer: a single unit (“mono”mer) of a polymer Macromolecule: a large organic molecule, made of polymers Four classes of macromolecules (biomolecules) – – – – Carbohydrates Lipids Proteins Nucleic Acids Each class of macromolecule possess The principle of POLYMERS How are monomers attached or detached? Dehydration Synthesis: polymerization reactions during which monomers are covalently linked, producing net removal of a water molecule for each covalent linkage Hydrolysis is a reaction process that breaks covalent bonds between monomers by the addition of water molecules. Carbohydrates (p60-): A monosaccharide (sugar) is the simplest kind of carbohydrate. It consists of a single molecule like fructose or glucose. All sugar molecules have the formula (CH2 O) n, where n is any number from 3 to 8. For glucose, n is 6, and its formula is C6H12O6 The formula for fructose is also C6H12O6 ά –glucose and - glucose: Two forms of glucose, seen below, differ only in a reversal of the H and OH on the first carbon. Even very small changes in the position of certain atoms may dramatically change the molecule Disaccharides Di (two) sacchar (sugar): a double sugar that consists of two monosaccharides joined by a glycosidic linkage. Glycosidic linkage: covalent bond formed by a condensation/dehydration (water is lost) reaction between two sugar monomers, for example maltose: Disaccarides – Common Disaccharides: Maltose= Glucose+Glucose (beer) Lactose= Glucose+Galactose (milk) Sucrose= Glucose+Fructose (table sugar/fruit sugar) – All saccharides are storage molecules, they store energy to be used by living system Storage Polysaccharides A polysaccharide consists of a series of connected monosaccharides. A polysaccharide is a polymer. Cells hydrolyze storage polysaccharides into sugars as needed. Common storage polysaccharides are STARCH, GLYCOGEN, CELLULOSE, and CHITIN. Starch: Starch is an ά-glucose polymer that is an energy storage molecule in plants Starch has two forms: – Amylose and Amylopectin Glycogen Glycogen: an ά-glucose polymer that is a storage polysaccharide in animal cells. Glycogen polymers are more tightly branched than starch Glycogen is stored in the muscle and liver of humans and other vertebrates Cellulose Cellulose is a polymer of - glucose molecules. It serves as a structural molecule in the walls of plant cells. Cellulose is the major component in wood. We are unable to digest Cellulose– Fiber in out diet Termites?? Starch vs. Cellulose What is the difference between starch and cellulose? Starch - ά-glucose polymer Cellulose - - glucose molecules. Figure 5.7x Starch and cellulose molecular models Glucose Glucose Cellulose Starch Chitin Chitin is a polymer similar to cellulose, but each -glucose molecule has a nitrogen containing group attached. Chitin serves as a structural molecule in the walls of fungus cells, exoskeletons of insects, and mollusks Lipids (p 65-) Lipids are a class of substances that are insoluble in water, but are soluble in non-polar substances (ether, chloroform) Fats are energy storage molecules, they store more energy per gram than carbohydrates! Lipids There are three major groups of lipids: – Triglycerides, phospholipids, and steroids – Triglycerides (fats, oils, waxes) – They consist of 3 fatty-acids attached to a glycerol molecule. – Fatty acids are hydrocarbon chains with a carboxyl group at one end of the chain Triglyceride/Fatty Acid: (type of lipid) A saturated fatty acid has a single covalent bond between each pair of carbon atoms, and each carbon has 2 hydrogen bonded to it. The carbon is “saturated” with hydrogen Unsaturated fatty acids have a double covalent bond and each of the two carbons in this bond have only one hydrogen atom bonded to it. Saturated vs. Unsaturated: Phospholipids (type of lipid) Phospholipids: look just like a lipid except that one of the fatty acid chains is replaced by a phosphate group (hence, “phospho” lipid) A phospholipid is amphipathic, meaning it has a hydrophobic “head” and hydophilic “tail” Phospholipids are oriented in a sandwich-like fashion formation with the tails grouped together on the inside (away from water) Steroids: (type of lipid) Steroids are characterized by a backbone of four linked carbon rings. Examples include cholesterol (a component of cell membranes), hormones, testosterone and estrogen. Proteins: (p79-) Proteins can be grouped according to their functions: Structural proteins: keratin, hair, horns, collagen, connective tissue, spider silk Storage proteins: casein in milk & ovalbumin in egg whites Transport proteins: found on cell membranes that transport materials into and out of cell, hemoglobin Defensive proteins: antibodies to fight infection Enzymes: regulate the rate of chemical reactions Protein -- Model… For a protein to function properly, it has to be folded into a specific structure. Protein folding has four levels of “folding” – Primary – Secondary – Tertiary – Quarternary Secondary Structure Secondary structure of a protein is a 3D shape that results from hydrogen bonding between the amino and carboxyl groups of adjacent amino acids. The bonding produces a spiral (alpha helix) The bonding produces a folded (pleated sheet) Proteins whose shape is dominated by these 2 patterns, form fibrous proteins Pages 82-83 Tertiary Structure Tertiary structure of a protein includes additional 3D shaping. The following factor contribute to tertiary “folding” – Hydrogen bonding between R groups of amino acids – Ionic bonding between R groups of amino acids – Hydrophobic effect – Disulfide Bonds, when the sulfur atoms in two cysteine amino acids bond….”Disulfide Bridge” Quaternary Structure Quaternary structure describes a protein that is assembled from two or more separate peptide chain. – Hemoglobin consists of 4 peptide chains held together by hydrogen bonding, R-groups interactions, and disulfide bonds Nucleic Acids The genetic information of a cell is stored in molecules of DNA. The DNA, in turn, passes its genetic instructions to RNA for directing various metabolic activities of the cell DNA is a polymer of nucleotides: – Nitrogen Base (A,T,C,G) – 5-carbon sugar (deoxyribose) – Phosphate group Purines and Pyrimidines The nitrogen bases are A, T, C, G A and G are “Purines” double-ring bases T and C are “Pyrimidines” single-ring bases You can remember which bases are purine because only the two purines end with “nine”: adenine and guanine Remember base pairing rules A-T and C-G Page 87 Nucleic Acids The two strands of DNA are antiparallel, that is, they run in opposite directions. One is arranged in the 5’3’ direction the other in the 3’5’ direction RNA RNA differs from DNA in the following ways: – The sugar in RNA is ribose, not deoxyribose – The thymine does not occur in RNA, it is replaced with uracil – RNA is a single-stranded molecule and does not form a double helix as DNA does.