Biology – Testing for biological molecules | e-Consult
Testing for biological molecules (1 questions)
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Apparatus:
- Test tube
- Dropper
- Sample containing the lipid (e.g., vegetable oil)
- Water
Procedure:
- Place a small amount of the sample containing the lipid in a test tube.
- Add a few drops of water to the test tube.
- Gently swirl the test tube.
Expected Results:
- Positive Result: A milky white emulsion will form. This indicates the presence of a lipid.
- Negative Result: The water and lipid will not mix, and the solution will remain clear. This indicates the absence of a significant amount of lipid.
Significance: The emulsion test is used to identify the presence of lipids in a sample. Lipids are insoluble in water, so they will form an emulsion when mixed with water, provided that they are present in sufficient quantities and are properly dispersed.
Factors affecting emulsion stability:
- Surface tension: Emulsifying agents (like soaps and detergents) reduce the surface tension between oil and water, allowing them to mix more easily and form a stable emulsion.
- Concentration of oil and water: A higher concentration of oil or water can affect the stability.
- Agitation: Continuous shaking or stirring helps to keep the oil dispersed in the water.
- Temperature: Temperature can affect the viscosity of the oil and water, which can influence emulsion stability.