Biochemical Test Essay

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Biochemical tests are used to detect the presence of different kinds of organic molecules, carbohydrates, lipids, nucleic acids, and proteins. These tests include the Benedict’s Test, Iodine Test, Sudan III Stain Test, Biuret Test and many others. With these tests, the nutrients from an unknown solutions can be identified in the solution.
The Benedict’s test is used for identifying reducing sugars, which are simple sugars that include monosaccharides and some disaccharides. The Benedict’s reagent is made of Copper (II) sulfate ion which reduces to Copper (I) during the test. It is made by adding copper sulfate with sodium citrate and carbonate that is dissolved in 400mLs of water (Benedict’s Test). The chemical reaction within this test is
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The iodine reagent is made by dissolving iodine in water mixed with 0.1 M potassium iodide, the bench iodine solution (What is the Iodine Test). Starch is made of bonds of amylose which is composed of a “straight chain of alpha glucose that are connected by alpha 1a4 glycosidic bonds” (Carbohydrates Test). With liquid food samples, 5 drops of iodine solution is dropped into the test tube. So, when the presence of starch is detected, the solution changes to a blue-black color because the starch-iodide combination absorbs light at different wavelengths, resulting in a strong purple color (Ophardt, Starch and Iodine). This type of reaction is made possible by the formation of polyiodide chains produced between the reaction of starch and iodine. If starch is not detected, the color remains unchanged (The Molecules of Life). This test is usually to find complex carbohydrates in foods or as a part of a photosynthesis experiment, which are both quantitative and qualitative datas. The only limitation of the Iodine test is that the test only identifies starch and not glycogen or cellulose which have bench iodine that appear to be a brown color, the control color (What is the Iodine …show more content…
The reaction involved in this test is between copper ions and peptide bonds in an alkaline solution. 0.395g of cupric sulfate and 1.51g of sodium potassium tartrate is dissolved in 100mL of water to make the Biuret reagent (Biologically Important). A positive testing for peptide bonds will result in the formation of a violet color. The color purple forms because when the copper (II) ions react with the lone electron pair of nitrogen in the Cu2+, it forms a “tetradentate” coordination complex within the four nitrogen giver atoms. When it is a negative result, the color of the solution remains unchanged and the color changes to pink when there is a small amount of peptide bonds found in the solution (Sundin, Proteins). The test merely identifies the presence of proteins in a sample but does not state the amount of proteins; further tests and comparisons must be done to figure the amount in unknown solutions. Spectroscopy, which uses visible radiation, is used to measure the quantitative data in the Biuret

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