Identifying Biological Molecules with Colorimetric Chemical Tests

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Identifying Biological Molecules with Colorimetric Chemical Tests

Objectives
Perform a series of accurate tests on biological molecules to detect the presence of carbohydrates and proteins, as well as the action of an enzyme on specific molecules.

Introduction
Unknown biological molecules can be correctly identified using various tests, including colorimetric chemical tests. Colorimetric tests are when a chemical reagent, such as Benedict’s, is used on a substance or solution and a certain color change occurs as a response. Carbohydrates and proteins, two of the larger types of biological molecules, also called macromolecules, are actually chains of molecules called polymers. The smaller molecules that build up these chains are called monomers. Proteins are chains of amino acid monomers. Enzymes are a type of protein that catalyzes or speeds up chemical reactions. The simplest and smallest carbohydrate is called a monosaccharide or simple sugar, and is a single monomer. Disaccharides are two monomers joined together and polysaccharides have three or more. Hydrolysis is a process that breaks down chains of polymers into monomers. In this experiment, we Benedict’s reagent was used both before and after hydrolysis, to identify reducing sugars, which includes both monosaccharaides and disaccharides. Benedict’s reagent changes color in the presence of reducing sugars as well as heat. Low concentrations of sugar yield a yellow to orange color while higher concentrations will be red to brown. Lugol’s solution was used before and after hydrolysis to identify polysaccharides. Proteins were tested for using Biuret’s reagent, the alkaline chemical compound CuSO4. The action of enzymes on specific molecules was also determined, using the enzyme invertase followed by another test with Benedict’s reagent.

Materials/ Methods
Please see pages 47-52 in the Bio lab manual.

Results:
In part 1 of this lab, we performed a series of tests on eight different...
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