The negative control used in the tests for protein, lipids, sugars, and starch was
A.
Albumin solution
B.
Starch solution
C.
Glucose solution
D.
Olive oil
E.
Distilled water
The Correct Answer and Explanation is:
Correct Answer: E. Distilled Water
Explanation:
In biochemical tests, negative controls are essential to ensure the reliability and validity of the experiment. A negative control is a sample that does not contain the substance being tested, and it is expected to produce no reaction or a baseline result. This helps to confirm that the positive results observed in the experimental samples are due to the presence of the substance being tested and not due to other factors, such as contamination or procedural errors.
For tests involving proteins, lipids, sugars, and starches, distilled water is commonly used as the negative control. Distilled water is pure H2O and does not contain any proteins, lipids, sugars, or starches. When used in biochemical tests, distilled water should yield a negative result, meaning there should be no color change or other reaction that would indicate the presence of these biomolecules.
- Protein Test (Biuret Test): The Biuret test is used to detect the presence of proteins. In the presence of proteins, the Biuret reagent changes color to purple. When distilled water is tested with Biuret reagent, no color change occurs, confirming the absence of proteins.
- Lipid Test (Sudan IV or Paper Test): The lipid test typically involves using Sudan IV or a paper test. Sudan IV stains lipids, and a positive result is indicated by a red-stained oil layer. Distilled water does not contain lipids, so there should be no staining or oil residue, confirming the absence of lipids.
- Sugar Test (Benedict’s Test): The Benedict’s test is used to detect reducing sugars. When reducing sugars are present, the Benedict’s solution changes color to green, yellow, orange, or red upon heating. Distilled water, lacking sugars, should remain blue (the original color of the Benedict’s solution).
- Starch Test (Iodine Test): The iodine test detects the presence of starch by changing color to blue-black in its presence. Distilled water should not cause any color change with iodine, confirming the absence of starch.
By using distilled water as a negative control, researchers can confidently determine whether the experimental samples contain the biomolecules of interest, ensuring the accuracy of their results.