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Identification of Organic Compounds

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Introduction

Biology 35 - Identification of Proteins, Carbohydrates and Fats Aim To figure out the unknown solution based on the results of the Benedict's reagent, Iodine solution, Biuret's solution, translucency test and Sudan IV solution with the known solutions. Problem Can the results of the different tests to determine the presence of reducing sugars, starch, proteins and lipid on known solutions be used to classify and determine the unknown solution? Hypothesis Given that the unknown substance is the same as one of the known substance, the unknown substance should exert similar properties with each of the tests than its known counterpart solution. Therefore, by looking at the results, we will be able to compare the unknown solution to one of the known solutions and classify it. Test for the Presence of Reducing Sugars (Benedict's Test) Background Information Benedict's reagent is used to determine the presence of simple sugars (monosaccharides and reducing sugars). Benedict's reagent is a chemical compound made up of copper sulfate, which can detect the presence simple sugars. A reagent is a chemical that is applied to another substance in order to produce a chemical reaction that can give valuable information regarding the substance. In order to test solutions with the Benedict's reagent, a small amount is added to the solution and then is boiled for several minutes to test the amount simple sugars present. The results will show precipitates within the tested substance. The precipitates show the amount of simple sugars present. Since the precipitates are likely to be very small, Benedict's reagent also shows the color changes that can gauge the amounts of the simple sugars. In the presence of simple sugars, the Benedict's reagent changes color to green, yellow, and brick-red, depending on the amount of simple sugar. Reducing sugar is oxidised when heated with Benedict's solution, which means the sugar looses electrons. Benedict's solution contains copper sulphate. The copper 2+ ions in copper sulphate gain an electron that the sugar has lost and become copper 1+ ions - this is called reduction. ...read more.

Middle

Conversely, sucrose, glucose, fructose, albumin, water, corn oil and the unknown solution did not have colors which would result if there was a presence of simple sugars. Going back to our hypothesis, the unknown solution has a possibility of being sucrose, glucose, fructose, albumin, water, or corn oil. Evaluation Our experiment in testing for the presence of starch using the Iodine solution was generally successful; however, there were several weaknesses with this method of testing the presence of starch using the Iodine solution. Some of the colors as a result of the Iodine solution were difficult to tell apart. One suggestion that could be made to improve this experiment would be to conduct several trials in order to ensure the validity of the colors recorded. Testing for the Presence of Proteins (Biuret Test) Background Information The Biuret solution is a mixture of copper sulfate and potassium hydroxide, which can detect the presence of proteins (specifically, peptide bonds). In order to test solutions with the Biuret solution, a small amount is added to the solution and then is shaken gently to test the amount simple sugars present. The results will show a ring of color within the tested substance. The color of the ring within the tested substance indicates whether or not proteins are present. In the presence of proteins, the Biuret solution changes the solution color from blue to pink-purple, depending on the amount of proteins present. In the presence of a peptide chain, four of the N atoms in the peptide bonds of 2 chains will form a complex with the Cu (II) ion in solution. This complexation causes a change in the electronical properties of the Cu ion, and results in the observed color change. This color change is dependant on the number of formed complexes, so longer chains will have a more pronounced color change. Problem Can the effect of the reaction of the Biuret solution to test for the presence of proteins with the known solutions be used to determine the unknown solution? ...read more.

Conclusion

Presence Of Lipids (Sudan IV) Sucrose Yes No No No - Glucose Yes No Yes No - Fructose Yes No No No - Starch No Yes No No - Albumin No No Yes No - Gelatin No Yes Yes Yes - Skim Milk Yes No Yes No - Water No No No No No Corn Oil No No No Yes Yes Unknown Yes No Yes No - Analysis Our hypothesis of whether or not we could figure out the identity of the unknown solution based on the results of the different tests with the known solutions was correct. The results above are a combination of all the data collected from the previous tests done. From the results, we can see that the unknown solution resulted positive for the presence of simple sugars and proteins, while resulting in negative (meaning no presence) for the presence of starch and lipids. From the known solutions, the only solutions that match this are skim milk and glucose. However, if we refer to the Iodine test portion of this lab, we see that the original color of the unknown solution was clear, ruling skim milk out. Therefore we can conclude that the unknown solution is glucose. However, in the Benedict and Biuret solutions, the results were a little different. This is because the glucose has been diluted with water. Evaluation Our experiment in generally, to find successful; however, there were several weaknesses with this method of testing for the unknown solution. Some of the colors of the different tests were difficult to tell apart. One suggestion that could be made to improve this experiment would be to conduct several trials in order to ensure the validity of the colors recorded. Another suggestion that could be made to improve this experiment would be to introduce experiments that don't necessarily deal with starches, proteins, sugars and lipids - for example, conductivity, as well as melting and boiling point tests. ?? ?? ?? ?? Carlos Jarquin April 17, 2009 BIO 35 - 8 BIO 35 - Identification of Proteins, Carbohydrates and Fats 1 ...read more.

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