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Identifying Biomolecules
Identifying Biomolecules
[MELC 22] Recognize the major categories of biomolecules such as carbohydrates, lipids, proteins, and nucleic acids. (S10MT-IVc-d-22)
Day 5: Identify biomolecules based on the result of physical and chemical tests or based on their function.
Identifying biomolecules involves analyzing their physical and chemical properties, as well as understanding their biological functions. Here are some common biomolecules and the methods used to identify them:
Physical and Chemical Tests for Biomolecules
Benedict’s Test (Simple Carbohydrates) - Used to identify reducing sugars (monosaccharides and some disaccharides). It identifies the presence of sugars in a sample by mixing it with Benedict's reagent and heating. A positive result shows a color change from blue to green, yellow, or orange to brick-red.
Iodine Test (Complex Carbohydrates) - Used to identify the presence of like starch. It identifies starch by adding iodine solution to the sample A positive result shows a color change from yellow-brown to blue-black.
Biuret Test (Protein) - Used to detect peptide bonds. It involves mixing the test sample with sodium hydroxide and copper sulfate solutions. A positive result shows a color change from blue to violet.
The Sudan IV (Lipids) - test is used to detect the presence of lipids. To perform the test, place the test solution in a test tube and add a few drops of Sudan IV dye. The mixture will separate into two layers, indicating the presence of a water-insoluble substance. The Sudan IV dye will color the lipids, and the appearance of a red color signifies the presence of lipids.
5. Emulsion test (Lipids) - To test for the presence of lipids, you would perform the emulsion test. Begin by mixing the sample with equal volumes of ethanol and water, then shake the mixture. If lipids are present, a cloudy white emulsion will form. If lipids are absent, no emulsion will be observed.
6. The Dische Diphenylamine Test (Nucleic Acid) - is used to detect DNA. To perform the test, add diphenylamine reagent to the sample solution in a test tube, then gently heat it in a boiling water bath for about 10 minutes. A positive result is indicated by the formation of a blue color, which signifies the presence of DNA
7. Methyl green-pyronin (MGP) (Nucleic Acid) is a classical histological staining technique that uses two cationic dyes to demonstrate and differentiate DNA and RNA. Methyl green specifically binds to the phosphate radicals in the DNA double helix, staining it green-blue. Result are Green-blue for DNA and red/pink for RNA.
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