Testing of biomolecules - Lab Report Example

Laboratory Techniques in the Study of Biomolecules Abstract Biomolecules are molecules that are produced by living organisms and which play certain roles in the life of the organism. They include proteins, carbohydrates, and nucleic acids and lipids. The knowledge of the organic molecules forms the basis in the study of biochemistry and medical sciences together with understanding how the body works. The body has a mechanism of ensuring that the molecules are regulated in the body and any deficiency is detected through various clinical manifestations. Some of the biomolecules are synthesized in the body while others are acquired through the food that we eat. For instance, when we come to amino acids which are the building blocks of proteins, they are divided into essential and non-essential ones. The essential ones are not synthesized in the body and so the body has to get them from the environment through the food that we eat. The various biomolecules play different roles in our bodies. The carbohydrates serve as the primary source of energy. They are divided into three groups, the monosaccharaides which are the simple sugars, the disaccharides which are formed by the dehydration process when two monosaccharide molecules are brought together. An example is the formation of lactose from glucose and galactose. Proteins are important in growth and repair. They also form the enzymes and hormones which are important in various catalytic metabolic processes in the body. Lipids serve in thermoregulation and as a source of energy while the nucleic acids, DNA and RNA are important in storage and transfer of genetic material in the body. Keywords: Carbohydrates, Proteins, Lipids, Nucleic Acids. Introduction The first step in the study of biomolecules is to test for their presence. There are different methods that have been developed to test for the presence of the biomolecules. It is important to know the presence of the biomolecules in various compounds for biochemical analysis. This is applied mainly in the analysis of the components of food products or when characterizing and quantifying nucleic acids in the laboratory. This report will therefore compile various methods that have been developed in the testing of biomolecules and depict the importance of each in biochemistry. The biomolecules that we shall look at include; - carbohydrates-three tests including the test for reducing sugars, test for non-reducing sugars, proteins, the tests analyzed will check for the presence of amino acids in the given samples. Amino acids are the building blocks for proteins and they are tested using the biuret method (John and Craney, p. 277). The tests for lipids and fats will be discussed and their importance highlighted. Lastly an analysis of nucleic acids will be done. The objective of this report is to have a deeper understanding in the writing of laboratory reports and also have a deeper understanding of biomolecules as important molecules of life. Methods This section will describe the methods used in the tests. All the methods will be discussed in prose and the results and discussion will follow. 1. Tests for Carbohydrates a. Reducing Sugars The most used method is the Benedict Solution Steps i. A beaker (250ml-300 ml) is filled with water heated gently. ii. The different samples are put in different test tubes and labelled. iii. About ten drops of Benedict’s solution is added to the samples. iv. The test tubes with the samples are placed in the hot water bath. v. The test tubes were removed after five minutes and color changes recorded. b. Non-reducing Sugars Disaccharides are formed when two monosaccharaides are brought together. In their tests a weak acid and water are used to hydrolyze them into reducing sugars. Steps i. Put about 250ml of water in a beaker and heat it over a Bunsen burner. ii. Put your samples in test tubes and remember to label them correctly. iii. Once the water is hot put the test tubes in it. iv. Add a few drops of the acid and later about ten drops of benedict’s solution. v. Record the color changes. c. Iodine test for starch (polysaccharide) i. Take the sample you want to test for the presence of starch and place it on a clean surface. ii. Onto it add a few drops of iodine solution. iii. Record the color changes. 2. Test for Proteins (Biuret Test) Amino acids are joined together by peptide bonds to form long and complex protein structure. This test is done to establish the presence of the peptide bonds. i. Put about 2 ml of the sample in a test tube. If there are more than one samples label the test tubes well to avoid confusion. ii. Add 2ml of Sodium Hydroxide into the samples and mix gently iii. Add a few drops of 1% Copper II Sulfate iv. Record the color change after a five minutes. 3. Test for lipids (Sudan IV Test) i. 2 ml of the unknown sample is placed in a test tube. ii. About five drops of the Sudan IV indicator is added. iii. A stopper is put to seal the test tube and then the contents shaken vigorously for about a minute. iv. Check for the formation of a ring at the top of the contents in the test tube. d. Test for Nucleic Acids (Dische Diphenylamine Test) This test is used to test for the presence of DNA in a given sample. i. Put 2 ml of the given sample in a test tube. ii. Add 2 ml of the Dische reagent and shake gently. iii. Check the color change. Results Reducing Sugars (Benedict’s Solution): Formation of a brick-red color indicates the presence of reducing sugars. If the color is green then the reducing sugars are absence. The color intensity is used to determine the amount of reducing sugars present. It may be green, yellow, and orange to brick red in the order of increasing amount of the reducing sugar. Non-reducing sugars: The color change is similar to that of the reducing sugars. Starch (polysaccharide): Formation of purple color indicates the presence of starch in the given sample. Biuret Test for Proteins: An analysis by Janairo & Marianne et. al. (2011), shows that if the color changes from blue to violet, proteins are confirmed present. No color change indicates the absence of proteins in the given sample. Sudan IV Test (Lipids): Formation of a ring at the top of the sample will indicate the presence of lipids. If there are no lipids present the dye will sink to the bottom of the test tube. Dische Diphenylamine Test (DNA): Formation of a blue color change indicates the presence of DNA in the sample. Discussion Reducing sugars contain the aldehyde groups in their structure. According to Wong (2011), when exposed to benedict’s solution which contains Cu2+ ions they are reduced to Cu+ ions with the formation of carboxylic acids from the initial sugar (p. 2-3). The brick red color seen is as result of the copper I oxide in the solution. This is insoluble in water and is used in the test to indicate the color change. In the test for non-reducing sugars, the water and acid are used to hydrolyze the bond formed when the monosaccharaides come together to form the disaccharide. One the bond has been broken, the reaction is similar to that in reducing sugars and the color changes expected are the same. In the test for starch, iodine solution is used. According to Becker and Media, (n.d), the formation of a blue color indicates the presence of starch. The blue color is formed due the reaction between starch and iodine to form the blue complex. While testing for proteins, the biuret test is used. The Biuret reagent contains aqueous copper II sulfate and sodium hydroxide mixed with potassium sodium tartrate. The formation of the blue to pink color is due to the formation of protein complexes. The target site is the peptide bonds which join the amino acids together. In the test for lipids, the Sudan IV dye which is soluble in lipids will move to the lipid layer and since its red in color dissolving in it will change its color to red. This will make it visible and hence conclude positively that there were lipids present in the solution. Deoxyribonucleic acid (DNA) contains a deoxyribose sugar while RNA contains a ribose sugar. This test uses this difference to test for the presence of DNA. The blue color formed is due to the reaction between the Dische reagent and the deoxyribose sugar. The color intensity is used to show the amount of DNA present in the sample. Conclusion Establishing the presence of various biomolecules serves as the bedrock of successive analyses which include the way they work in the body. It is therefore important to understand the preliminary tests before understanding the various steps that follow. It is also important to note that there are other methods used to achieve similar results while identifying the various biomolecules. References Becker, A. and Media, D. (n.d). Lab Experiments to Test for the Presence of Starch when Using Potassium Iodine. Web. Available at. Janairo, G., Marianne, L. S., Yap, L., Lazaro,-Llanos, N. and Robles, J. (2011). Determination of the Sensitivity Range of Biuret Test for Undergraduate Biochemistry Experiments. E-journal of Science & Technology (e-JST). 5(6), 78. Johnson, R. M., and Craney, E. C. (1971). Rapid Biuret Method for Protein Content in Grains. American Association of Cereal Chemists. (48), 277. Wong, S. (2011). Reducing Sugars Lab Report. 2-5. Available at. (n.a). The Lab of Exploring Biomolecules. Available at. Acknowledgments Read More