Biology: Chemical Tests and Test

Topics: Chemical tests, Benedict's reagent, Reducing sugar Pages: 8 (2049 words) Published: October 24, 2010
Biology 100 Lab
Laboratory Report
Title: Identifying the four major classes of macromolecules through various tests. Group Members: Antonia Johnson, Payton Ewing, Lenneisha Hepburn, Kendisha Hanna,  
 Macromolecules also known as biological molecules are monomers which are the simple units of polymers. All macromolecules contain carbon and hydrogen which are found in organic compounds. In this Experiment we will test for the presence of protein, starch, lipids, and sugars by analyzing the content off food and / or other substances by utilizing different testing methods. In the scientific method, a chemical test that is sensitive to these groups can be used to identify molecules that are in that class. Testing involves many procedures that are very precise. This lab is broken down into five different sections; we will be using the Biuret Test for amino groups present in proteins. The Iodine Test to identify the presence of starch. The Grease Spot Test and the Sudan Dye test to identify the presence of lipids (fatty acids). The Benedict’s Test to identify the presence of reducing sugars. In the biuret test if the test result for protein changes a color of lavender, purple or pink, the test result for protein is positive using the Biuret reagent. In the iodine test If the Iodine turns black or blue-black there is starch present so the test result is positive. In the grease spot test if the test results leaves a translucent mark on the unglazed paper it is positive for the presence of lipids. In the Sudan test if the globules have red dye within them the test result is positive; this means there is lipids present in this test. For the Benedicts test if the substance turns from a blue liquid to a greenish to yellow/orange/red shows the presence of a reducing sugar.   BENEDICT'S TEST

Introduction: Monosaccharaides and disaccharides can be detected because of their free aldehyde groups, thus, testing positive for the Benedict's test. Such sugar acts as a reducing agent, and is called a reducing sugar. By mixing the sugar solution with the Benedict's solution and adding heat, an oxidation- reduction reaction will occur. The sugar will oxidize, gaining oxygen, and the Benedict's reagent will reduce, losing oxygen. If the resulting solution is red orange, it tests positive, a change to green indicates a smaller amount of reducing sugar, and if it remains blue, it tests negative.

Introduction: The iodine test is used to distinguish starch from monosaccharaides, disaccharides, and other polysaccharides. Because of its unique coiled geometric configuration, it reacts with iodine to produce a blue- black color and tests positive. A yellowish brown color indicates that the test is negative.


Introduction: Sudan test detects the hydrocarbon groups that are remaining in the molecule. Due to the fact that the hydrocarbon groups are nonpolar, and stick tightly together with their polar surroundings, it is called a hydrophobic interaction and this is the basis for the Sudan test. If the end result is a visible orange, it tests positive.


Introduction: In a peptide bond of a protein, the bond amino group is sufficiently reactive to change the Biuret reagent from blue to purple. This test is based on the interaction between the copper ions in the Biuret reagent and the amino groups in the peptide bonds.

Introduction: Lipids are non-water-soluble organic compounds that are found in many foods. If you are concerned about excessive fats in your diet you can check for lipids to reduce your intake. As we all know from experience, lipids leave translucent spots (grease spots) on unglazed brown paper bags.  


Materials/ Apparatus                                  * Biuret Reagent
* Benedict’s Solution
*  Sudan Dye IV
*  Glucose (10%, 25%, 50%)
*  Iodine
*  Thermometer
*  Beaker
*  Droppers
*  Sucrose (10%)
*  Egg...
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