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EX 5

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Benedict’s TestIodine Starch TestBiuret TestGrease-Spot testYK.a.00 EX 5 Biologically Important Molecules Among other biologically important molecules and compounds, these four compounds are the most abundant and important for any life forms. The details are left for lecture in 1710 and upper level courses, and we will survey their basic characteristics and importance of testing and experiment standards in science. Objectives: 1. There are always certain large organic molecules involved in biological systems. We will survey Carbohydrates, Proteins, Lipids, and Nucleic Acids. 2. Although this lab is not designed for you to memorize structures of these macromolecules, it is for you to recognize basic and common feature of them. 3. Through the tests you may conduct, you will understand meaning and purposes of basic set for an experiment, unknown sample and controls. 4. Learn about a few tests. A Set for an Experiment: In order to verify either an experiment worked or failed, scientists have developed a basic set for experiments, unknown and controls. Unknown = Solution or sample to be examined. Where expected compounds are there or not is unknown. Control = Controls are to compare the results from unknown to verify if experiment worked or not. Their results are fixed. There are two controls, positive and negative. Positive control = Contains expected compound to be in the unknown. For example, if you are detecting lipids in unknown, the positive control contains these lipids. Negative control = Does not contains expected compound. For example, detecting lipids, the negative control does not contain any lipids. ¾ Whenever you do an experiment, consider what is positive / negative control, and what is unknown!! Carbohydrates: The simplest unit of carbohydrates is simplest sugar or monosaccharide, such as glucose, fluctose, etc. Their molecules are made out of carbon (C), Hydrogen (H), and oxygen (O), and their ratios are C:H:O = 1:2:1. Each monosaccharide is bound together by dehydrolysis, and form disaccharide and polysaccharides, starch, glycogen and cellulose. Bio-molecules composed of carbohydrates (fig 5.1 & 5.2) The shape of sugar chains determines name of molecules. • monosaccaride = glucose • disaccharide = sucrose (table sugar) • polysaccharide = cellulose Chemical bond of carbohydrates (fig. 5.3) • Hydrolysis = ‘Add’ or ‘insert’ a water molecule and ‘break’ a bond. • Dehydrolysis = ‘Remove’ a water molecule, and create a ‘binding’.YK.a.00 Benedict’s Test Color of indicator : Green ---------------------------------------- Red/Orange Amount of reduced sugars. More Less (= enrich in smaller sugars) Iodine Starch Test Color of indicator: Purple ----------------------- Brown/Black Presence of Starch: (Negative) (Positive ) Proteins: The smallest unit of a protein is amino acid, has amino group (-NH3+) and carboxyl group (-COOH). Bond between amino acids is called peptide bond (fig 5.6). There are more than 20 amino acids used by organisms. You can imagine these 20 amino acids as Lego© bricks. Molecules composed of proteins (fig 5.4) Ways of using different kind of amino acids and length of their chains allow proteins having so many types of features and characteristics. • Hair • Collagen Tennis strings, skins • Fibrin = Fiber for immune system • Keratin = Birds’ feather • Silks = Spiders and other insects Biuret Test Intensity of purple color: Dark/ Intense --------------- Light Amount of Peptide bonds: More Less Lipids: They contains many hydrocarbons hence hydrophobic (not be dissolve in water), but are dissolved in non-polar solvents, ether, acetone, etc in general. In this exercise we will focus on triglycerides as representative of lipids (fig 5.7). Sudan IV test Intensity of color: Dark/ Intense --------------- Light Amount of Peptide bonds: More Less Grease-Spot test Translucent: More ------------------------ Less Amount of lipids: More Less Nucleic Acids: DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid) are composed of phosphate, pentose sugar, and base (either purines or pyrimidines). They are the program and database of the life. Unique combination of bases makes life to function. Dische diphenylamine test Deoxyribose (in acid) + diphenylamine Æ Blue complex Intensity of blue: None ------------------------------------ Dark blue None


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