Experiment 4: Qualitative Tests for Lipids PDF

Summary

This document is a laboratory manual for an experiment on qualitative tests for lipids. The experiment involves determining the solubility and unsaturation of different lipid samples using various solvents and tests. The document is suitable for undergraduate-level students in chemistry or biology.

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Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL Experiment 4: Qualitative Tests for Carbohydrates I. Objectives...

Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL Experiment 4: Qualitative Tests for Carbohydrates I. Objectives At the end of the experiment, the student should be able to: 1. Distinguish different oils and fats of commercially available lipids based on the qualitative tests 2. Learn the chemical basis of each chemical tests II. Introduction Lipid is a class of biological molecules defined by low solubility in water and high solubility in non-polar solvents. Unlike other biomolecules, lipids do not have a common structural feature that serves as the basis for defining such compounds, but they can be grouped based on their solubility in nonpolar organic solvents such as hexane, petroleum ether, and dichloromethane. Lipids has a wide array of functions, it could be used for storage of energy – lipids represent highly reduced forms of carbon and, upon oxidation in metabolism, yield large amounts of energy, making them molecules of choice for metabolic energy storage. It is also a membrane component which provides insoluble compartments in the cell that contains aqueous solutions. Lipids can also serve as chemical messengers. Triacylglycerols are considered the energy providing lipid, it is more efficient than other energy storage in biological systems. It is composed of three fatty acid molecules attached to a glycerol backbone through ester bonds. Aside from providing energy, triacylglycerols are derivatives of cell membrane lipids (phosphoacylglycerols and sphingolipids), as well as the waxes found in the leaves of plants produced by some animals. It is then important for humans and other organisms to receive an adequate amount of triacylglycerols in the diet. Dietary sources of lipids come from various plant and animal sources. Oils are of plant origin and are liquid at room temperature. Fats, on the other hand, are of animal origin and are solid to semi-solid at room temperature. This occurs due to the degree of unsaturation found in the fatty acid components. Lipids can be extracted from cells and tissue by non-polar solvents like ether, chloroform, benzene, etc. The non-polar solvents are known as fat solvents. Lipids that contain fatty acid components are saponifiable. Some lipids such as sterols are non-saponifiable. 1 Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL III. Apparatus Pasteuer pipette Serological pipette Graduated cylinder Iron ring and stand Bunsen burner Wire gauze Stirring rod Evaporating dish Beaker Test tubes Aspirator Test tube rack Water bath Thermometer IV. Reagents Chloroform Benzene Ethanol Hexane Butanol 2 M NaOH I2 solution Palmitic acid Na2CO3 Coconut oil (Virgin Coconut Oil) Diethyl ether Olive oil Potassium hydrogen sulfate Vegetable oil V. Procedure A. Solubility 1. In each test tube, place 1 mL of the following fat solvents: hexane, benzene, ethanol, butanol, diluted sodium hydroxide, and water 2. Add a drop of the oil and shake well in each test tube. 3. Observe if there is presence of layers or you only see I phase of the combined substances. Record your observation. 4. Repeat the procedure for all lipid samples B. Translucent Test 1. Fold your filter paper into 3 equal parts. 2 Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL 2. Using a dropper, drop the oil on one part, then drop the alcohol on the second part, and drop the ether on the third part of the filter paper. 3. After few minutes, note the drop made on the filter paper by holding it up to the light. 4. Repeat the procedure for all lipid samples C. Test for Unsaturation 1. Prepare four (4) test tubes as follows: First tube- one drop olive oil Second tube- one drop coconut oil Third tube- one drop vegetable oil Fourth tube- a pinch of palmitic acid 2. Dispense 1mL of chloroform to each tube and mix well. 3. Add iodine solution dropwise. 4. Take note of the number of drops used until yellow color persists. D. Acrolein Test 1. Place 1 mL of coconut oil, vegetable oil, and olive oil in three different evaporating dish 2. Add few crystals of potassium hydrogen sulfate 3. Warm gently to mix and then heat strongly. 4. Observed the occurrence of pungent odor indicate of acrolein formation 5. Repeat the procedure for all lipid samples. E. Saponification Test 1. Take a sample of lipid in a test tube. 2. Then, add sodium hydroxide (at least 2M). 3. Then, boil the solution in a water bath for 5 minutes. 3 Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL 4. At last, add ethanol. 5. Observe the test tube for the appearance of froth. 6. Repeat the procedure for all lipid samples. F. Emulsification of Fats 1. Prepare three (3) tubes as follows: Tube 1- 1 mL water + 1 drop coconut oil Tube 2- 1 mL water + 1 drop coconut oil + 1 drop Na2CO3 solution Tube 3- 1 mL water + 1 drop coconut oil + a pinch of soap. 2. Shake vigorously each tube for two minutes and observe the result immediately. 4 Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL DATA SHEET Experiment 4: Qualitative Tests for Lipids A. Solubility Tests Samples Hexane Benzene Ethanol Butanol Water NaOH Olive Oil Coconut Oil Vegetable oil B. Translucent Test Observations: C. Test for Unsaturation Lipid Samples Drops of Iodine Used Olive Oil Coconut Oil 5 Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL Vegetable oil Palmitic Acid Chemical Equation Involved: D. Acrolein Test Observations: Chemical Equation Involved: E. Saponification Observations: Chemical Equation Involved: F. Emulsification Observations: 1. coconut oil 6 Far Eastern University Institute of Arts and Sciences MTY1107 / BIO1106 Department of Mathematics LABORATORY MANUAL 2. coconut oil + Na2CO3 solution 3. coconut oil + a pinch of soap Chemical Equation Involved: 7

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