Biochemistry Laboratory - CH 601L (2011-2012) Experiment 6
Characterization of Saponifiable Lipids
Kevin Arven A. Benin*, and Gabrielle Marie A. Bugna
Department of Chemistry, College of Science
University of Santo Tomas, Espana Street, Manila 1050
Date Submitted: August 25, 2011
________________________________________________________________________ Abstract: The experiment was about the characterization of a fat/oil sample through three tests, namely the grease-spot test, saponification test, and unsaturation test. The procedures include the use of a filter paper divided into four sections and a drop of vegetable oil in a section; the same was done on lecithin, dichloromethane, and water and was heated. Oil, fat, and water were subjected into a saponification test using NaOH, and acidification using concentrated H2SO4. And lastly, oil, fat and glycerol were subjected into an unsaturation test by adding dichloromethane, and was added with a 5% Bromine-dichloromethane solution, the total volume of the 5% Br-DCM solution was then obtained.
Lipids are a group of the essential biomolecules in which are generally characterized by their insolubility in water, and are soluble in ethers, alcohols, and other fat solvents (Hawk, 1954). Lipids are classified into three classifications, simple, compound or conjugated, and derived lipids. Simple lipids are esters of fatty acids with various alcohols. Compound or conjugated lipids are esters of fatty acids containing groups in addition to an alcohol and a fatty acid. Derived lipids are those derived from simple/compound lipids through hydrolysis (Harper et al., 1977). Christie (2010) defined lipids as fatty acids and their derivatives, and substances related biosynthetically or functionally to these compounds. In this experiment, only the simple lipids are of focus.
The main biological functions of lipids include energy storage, as structural components of cell membranes, and as important signaling molecules. Lipids are a variety of organic molecules grouped together on the basis of their solubility in non -polar solvents. Their varied biological functions include energy source, energy storage, cell membrane structural components, hormones, vitamins, vitamin adsorption, protection, and insulation.
Saponification refers to the hydrolysis of fatty acid ester bonds by a strong base/alkali as a catalyst. Saponification of triglycerides, in which is a simple lipid produces glycerol and fatty acid salts, and these salts are called as “soaps”. The term saponification is derived from the Latin words sapon which means “soap” and the suffix “-ficare” which means “to do” or “make”
Figure 1: The Saponification reaction of a triglyceride with a strong base (NaOH)
2. Experimental Section
The experiment was divided into three (3) parts, namely the grease-spot test, the saponification test, and the unsaturation test.
The first part, the grease-spot test. First, a piece of filter paper was obtained and was divided into four sections, namely, lecithin, vegetable oil, dichloromethane, and water. Second, a drop of lecithin was placed in the section named lecithin; the same procedure was done on dichloromethane, vegetable oil, and water on their respective sections. The filter paper was heated on a hot plate on its lowest setting. All observations were then recorded,
The second part, the saponification test starts with three (3) test tubes labeled as “oil”, “fat”. And “water”. 8 drops of oil, fat and water were placed in their respective tubes. 10 drops of NaOH was then added to all three tubes and heated at a boiling water bath for 15-20 minutes. After heating, the tubes were cooled to room temperature. 5 mL of distilled water was placed into the...