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We were given 5 solutions labelled A, B, C, D and E. We were told that there was a reducing sugar, starch, non-reducing sugar, lipid and protein. My aim was to carry out some standard tests on these solutions and identify them as appropriate.

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Introduction

Introduction We were given 5 solutions labelled A, B, C, D and E. We were told that there was a reducing sugar, starch, non-reducing sugar, lipid and protein. My aim was to carry out some standard tests on these solutions and identify them as appropriate. Method I will perform a standard test on each solution until they prove conclusive upon which I will move to the next solution. The tests are dteialed below and it is the order I followed on each solution. Background to Test 1: Reducing Sugar Test All monosaccharides and some disaccharides are reducing sugars. The test for a reducing sugar is known as the Benedicts test. When a reducing sugar is heated with an alkaline solution of copper II sulphate it forms an insoluble precipitate of copper I oxide. ...read more.

Middle

of NaOH * Add 1cm3 of Benedicts solution * Heat in water bath * Record any colour change Background to Test 3: Starch Starch is easily detected by its ability to turn iodine in potassium iodide solution from a yellow colour to blue-black. The colouration is due to the iodine molecules becoming fixed in the centre of the helix of each starch molecule. It is important to do the test in room temperature as high temperature cause the starch helix to unwind which releases the iodine and assumes its usual yellow colouration. Test 3 * Take a couple of drops of test solution and put in spotting tile * Add a few drops of iodine * Record any colour change Background to Test 4: Lipids The test for lipids is known as the emulsion test. ...read more.

Conclusion

First to a sample of the solution add an equal volume of sodium hydroxide. Secondly, add a few drops of very dilute (0.05%) copper II sulphate solution and mix gently. A purple colouration indicates the presence of peptide bonds and hence a protein. Test 5 * Put 1cm3 of test solution in test tube * Add biuret solution * Record colour change Results Table Solution Reducing Sugar Non-Reducing Sugar Starch Lipid Protein A Purple X B Brown X C Cloudy X D Black X E Brown X Conclusion I performed the tests as described in numerical order. If for example a test proved positive on Test 2, then I did not carry on with Test 3 and so on. My results are show above, it shows that solution A was a protein, solution B was a reducing sugar, solution C was a lipid, solution D was a starch and solution E was a non-reducing sugar. ...read more.

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