BIOCHEMICAL TESTS- Test for Starch, Reducing Sugars, non-Reducing Sugars, Proteins, Lipids

Biochemical Tests

The biochemical tests conducted in this lab are to test the presence of carbohydrates, proteins, and lipids. Three types of carbohydrates will be tested namely starch, reducing sugar (glucose), and non-reducing sugar (sucrose). The test for checking the presence of starch is demonstrated first. Add iodine which is of brownish-orange color to a sample of starch in a test tube. As a result, the solution would turn bluish-black establishing the presence of starch. Next, the test for reducing sugar is conducted by adding Benedict’s solution to a test tube filled with distilled water and another filled with glucose. Upon heating the two test tubes, the solution of distilled water will remain blue while the glucose solution will change color from blue to orange. A green-yellow color would indicate low concentration while a bright red color depicts a high concentration of reducing sugar. Another carbohydrate, the non-reducing sugar is tested through sucrose. First, Benedict’s test will be conducted to prove that it is a non-reducing sugar. Later acid is added to the sample of sucrose and boiled to a hundred degrees while monitoring the temperature through a thermometer. This process is known as acid hydrolysis. After cooling the solution, an alkali is added to neutralize it. Next, add Benedict’s solution and heat it. As a result, the solution will form brick red precipitates showing the presence of reducing sugar.

For the test of proteins, add biuret to albumin. Since albumin is a protein, the solution would turn from blue to purplish lilac color. For the last test, that is for lipids, dissolve ethanol in a lipid, i.e., oil. Shake it and add distilled water. Shake it once again. As a result, a white emulsion will be formed proving the presence of lipids. Conclusively, an iodine test is conducted for carbohydrates, an emulsion test is conducted for lips and a biuret test is conducted for proteins.

References

Estruch, M. (n.d.). A-level BIOCHEMICAL TESTS- test for starch, reducing sugars, non-reducing sugars, proteins, lipids. Retrieved from https://www.youtube.com/watch?v=5BkPVT1-nwc