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Questions and Answers
What is the primary purpose of lipids in the body?
What is the primary purpose of lipids in the body?
- Protein synthesis
- Energy storage (correct)
- Oxygen transport
- Carbohydrate breakdown
Lipids are only used for energy storage in the body.
Lipids are only used for energy storage in the body.
False (B)
Name one qualitative test used for the presence of lipids.
Name one qualitative test used for the presence of lipids.
Acrolein Test
The process of extracting lipids from egg yolk involves using __________ to dissolve the lipids.
The process of extracting lipids from egg yolk involves using __________ to dissolve the lipids.
Match the following lipid tests with their associated characteristics:
Match the following lipid tests with their associated characteristics:
What substance is added to the lipid solution in the Libermann-Buchard Test?
What substance is added to the lipid solution in the Libermann-Buchard Test?
The Spot Test involves placing a drop of lipid solution directly into a test tube.
The Spot Test involves placing a drop of lipid solution directly into a test tube.
How long should the mixture stand during the lipid extraction process?
How long should the mixture stand during the lipid extraction process?
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Study Notes
Lipids: Properties and Extraction
- Lipids are amphipathic molecules including fatty acids, triglycerides, phospholipids, and cholesterol.
- They provide energy, act as chemical messengers, maintain body temperature, aid in membrane and prostaglandin formation, and mediate inflammation.
Experiment Objectives
- Extract lipids from egg yolk.
- Perform qualitative tests (Acrolein, Libermann-Buchard, Spot Test, Unsaturation Test) to identify lipids.
- Analyze the principles behind the lipid reactions in each test.
Materials
- Laboratory Equipment: Beaker, test tube, test tube rack, funnel, filter paper, alcohol lamp, watch glass.
- Sample: 2g of cooked egg yolk (from 2 large hard-boiled eggs).
- Reagents: 2-propanol, acetic anhydride, glacial acetic acid, Lugol’s solution, potassium bisulfite, sulfuric acid.
Lipid Extraction Procedure
- Weigh 2g of cooked egg yolk.
- Add 10 mL of 2-propanol, stir, and cover to prevent evaporation.
- Let stand for 10 minutes, stirring frequently.
- Filter the mixture to separate liquid and solid components.
- Evaporate the solvent (in a fume hood) to concentrate the filtrate.
- Weigh the recovered lipid residue.
- Dissolve the residue in 1 mL of glacial acetic acid. This solution is used in subsequent tests.
Acrolein Test
- Add 10 drops of lipid solution and potassium bisulfite to a test tube.
- Heat until fumes form; observe the odor (characteristic of acrolein, indicating the presence of glycerol).
Libermann-Buchard Test
- Add 10 drops of lipid solution, 4 drops of acetic anhydride, and 1 drop of sulfuric acid to a test tube.
- Observe color changes (indicates the presence of cholesterol).
Spot Test
- Place a drop of lipid solution on filter paper.
- Observe the spot after 5 minutes (a translucent spot indicates the presence of lipids).
Unsaturation Test
- Add iodine solution dropwise to 10 drops of lipid solution while shaking.
- Note the amount of iodine needed to turn the solution light orange (indicates the degree of unsaturation in fatty acids).
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