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BIOL 1020 (101)

BIOL 1020 5

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BIOL 1020
Anne- Marie Singh

BIOL 1020 – CHAPTER 5 LECTURE NOTES Chapter 5: The structure and function of macromolecules I. many biological molecules are polymers a. polymers are long chains or branching chains based on repeating subunits (monomers) i. example: proteins (the polymer) are made from amino acids (the monomers) ii. example: nucleic acids (the polymer) are made from nucleotides (the monomers) b. very large polymers (hundreds of subunits or more ) are called macromolecules c. polymers are degraded into monomers by hydrolysis (“break with water”) i. typically requires an enzyme to occur at a decent rate ii. hydrogen from water is attached to one monomer, and a hydroxyl from water is attached to the other d. monomers are covalently linked to form polymers by condensation i. also typically requires an enzyme to occur at a decent rate ii. typically the equivalent of a water molecule is removed (dehydration synthesis) II. The four major classes of biologically important organic molecules are: carbohydrates, lipids, proteins, or polypeptides (and related compounds), and nucleic acids (and related compounds) III. carbohydrates include sugars, starches, and cellulose A. carbohydrates contain only the elements carbon, hydrogen, and oxygen B. the ratio works out so that carbohydrates are typically (CH2O)n C. carbohydrates are the main molecules in biological systems created for energy storage and consumed forenergy production; some are also used as building materials D. grouped into monosaccharides, disaccharides, and polysaccharides 1. monosaccharides are simple sugars (a single monomer) • have 3, 4, 5, 6, or 7 carbons • referred to as trioses, tetroses, pentoses, hexoses, and heptoses • examples of pentoses include ribose and deoxyribose (part of nucleic acids) • examples of hexoses include glucose, fructose, and galactose; glucose is most abundant • Examine the structural formulas for glucose, fructose, and galactose. Note that they are all isomers of each other (i.e. they have the chemical formula C6H12O6). Glucose and galactose are structural isomers of fructose, while glucose and galactose are diastereomers (a type of stereoisomer). • pentose and hexose sugars actually form ring structures in solution this often creates diastereomersexample: -glucose and -glucosenote how carbons are given numbers to indicate position 2. disaccharides consist of two monosaccharide units • the two monomers are joined by a glycosidic linkage or glycosidic bond • formed when the equivalent of a water molecule is removed from the two monosaccharides • an oxygen atom is bound to a carbon from each momomer • typically, the linkage is between carbon 1 of one and 4 of the other • maltose, sucrose, and lactose are common disaccharides maltose (malt sugar): has two glucose subunits sucrose (table sugar): glucose + fructoselactose (milk sugar): glucose + galactose • maltose sucrose and lactose • maltose (malt sugar; two glucose subunits • sucrose (table sugar) glucose+fructose • lactose (milk sugar) glucose+galactose 3. polysaccharides are macromolecules made of repeating monosaccharides units linked together by glycosidic bonds • number of subunits varies, typically thousands • can be branched or unbranched • some are easily broken down and are good for energy storage (examples: starch, glycogen) polymer of alpha glucose • some are harder to break down and are good as structural components (example: cellulose) polymer of beta glucose • starch is the main storage carbohydrate of plants polymer made from α-glucose units linked primarily between carbons 1 and 4 amylose = unbranched starch chain (only have α1-4 linkages) amylopectin = branched starch chain (branches by linkages between carbons 1 and 6) plants store starches in organelles called amyloplasts, a type of plastid • glycogen is the main storage carbohydrate of animalssimilar to starch, but very highly branched and more water-solubleis NOT stored in an organelle; mostly found in liver and muscle cells • cellulose is the major structural component of most plant cell wallspolymer made from beta-glucose units linked primarily between carbons 1 and 4 (similar to starch, but note that the 1-4 linkage makes a huge difference)unlike starch, most organisms cannot digest cellulosecellulose is a major constituent of cotton, wood, and papercellulose contains ~50% of the carbon in found in plantsfibrous cellulose is the “fiber” in your dietsome fungi, bacteria, and protozoa make enzymes that can break down celluloseanimals that live on materials rich in cellulose, e.g. cattle, sheep and termites, contain microorganisms in their gut that are able to break down cellulose for use by the animal 4. carbohydrates can be modified from the basic (CH2O)n formula • many modified carbohydrates have important biological roles • example: chitin – structural component in fungal cell walls and arthropod exoskeletons • example: galactosamine in cartilage • example: glycoproteins and glycolipids in cellular membranes IV. lipids are fats and fat-like substances E. lipids are a heterogeneous group of compounds defined by solubility, not structure F. oily or fatty compounds G. lipids are principally hydrophobic, and are relatively insoluble in water (some do have polar and nonpolar regions)1. lipids consist mainly of carbon and hydrogen2. some oxygen and/or phosphorus, mainly in the polar regions of lipids that have such regions H. roles of lipids include serving as membrane structural components, as signaling molecules, and as energy storage molecules I. major classes of lipids that you need to know are triacylglycerols (fats), phospholipids, and terpenes J. triacylglycerols contain glycerol joined to three fatty acids 1. glycerol is a three carbon alcohol with 3 -OH groups 2. a fatty acid is a long, unbranched hydrocarbon chain carboxyl group at one end • saturated fatty acids contain no carbon-carbon double bonds (usually solid at room temp) • unsaturated fatty acids contain one or more double bonds (usually liquid at room temp) monounsaturated – one double bondpolyunsaturated – more than one double bond • about 30 different fatty acids are commonly found in triacylglycerols; most have an even number of carbons 3. condensation results in an ester linkage between a fatty acid and the glycerol • one attached fatty acid = monoacylglycerol • two = diacylglycerol • three = triacylglycerol 4. triacylglycerols (also called triglycerides) are the most abundant lipids, and are important sources of energy G. phospholipids consist of a diacylglycerol molecule, a phosphate group esterified to the third -OH group of glycerol, and an organic molecule (usually charged or polar) esterified to the phosphate 1. phospholipids are amphipathic; they have a nonpolar end (the two fatty a
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