Determination of Presence of Protein

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Determination of presence of protein in a variety of food substances by the use of Biuret Reagent Biol. 1040 Section 1005 Introduction The human body consumes carbohydrates, lipids, and proteins each day by eating a variety of foods. These foods are required for energy and human growth. Proteins are a diverse group of macromolecules with many different functions (Mbuthia, 2012). Many are structural components of bone, muscle, hair, tissue, etc. Others are enzymes that speed up cellular reactions. All proteins are made up of amino acids (Johnson, 2010).

The purpose of this experiment is to determine whether peptide bonds are present in various food substances. The color violet will indicate the presence of proteins. The more intense the color is, the greater number of peptide bonds there are (Mbuthia, 2012). Methods Using the China marker, I numbered test tubes 1-5 for identification purposes. Using a pipet I added 1 milliliter of each solution to it’s designated test tube. Next, I added 5 drops of the Biuret reagent to each test tube and agitated the mixture by shaking the tubes from side to side.

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After waiting 2 minutes I recorded the color of each mixture. I used the color reaction after adding the reagent to determine the presence of proteins in each substance (Mbuthia, 2012). Results Test solutions that contained proteins reacted to the Biuret reagent by turning violet. Table 1 summarizes the test results. In summary, test solutions, including distilled water, as a control, starch, glucose, and soft drink did not contain proteins. Egg albumin was the only test solution that contained proteins. Table 1 |Tube |Contents |Color

Reaction |Conclusion | |1 |Distilled Water |Clear/Blue |Did not contain protein | |2 |Starch |Cloudy Blue |Did not contain protein | |3 |Egg Albumin |Violet |Contained protein | |4 |Glucose |Clear/Blue |Did not contain protein | |5 |Soft Drink |Clear/Yellow |Did not contain protein | Discussion

These results indicate that all of the test solutions, except the egg albumin, did not contain protein. These results support the hypothesis that if proteins are present in the food substances that they will react with the Biuret reagent, causing the solution to turn a shade of violet. Distilled water was used as a control in this experiment, providing a basis for comparison. Food substances that did not turn a shade of violet indicate that they did not contain proteins, which happened to be most of the substances in this experiment. Works Cited 1. Johnson, G. B. 2010. Essentials of the Living World. McGraw Hill companies. 2. Mbuthia, K. W. 2012. Laboratory Manual for Introduction to Biology 1040. Thomson Publishing Company.

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