BIO_LAB

• What are lipids classified as?

  Amphipathic molecules
• What are some examples of lipids?

  Fatty acids, diglycerides, triglycerides, phospholipids, and cholesterol
• What role do lipids play in the human body?

  They provide energy, act as chemical messengers, maintain body temperature, form membrane layers, and mediate inflammation
• What materials, reagents, and equipment are needed for lipid extraction from egg yolk?

  • Beaker
  • Test tubes
  • Test tube rack
  • Test tube holder
  • Filter paper
  • Funnel
  • Petri dish
  • Graduated cylinder
  • Stirring rod
  • Tripod
  • Egg yolk
  • Acetone
  • Ethanol
  • Chloroform
  • Centrifuge
• What are the steps for extracting lipids from egg yolk?

  1. Collect egg yolk from 2 eggs and mix well.
  2. Add 50mL of cold acetone and mix, then let stand for 15 mins.
  3. Centrifuge for 5 min at 4000 rpm to collect precipitate.
  4. Wash precipitate with acetone until supernatant is clear.
  5. Extract with chloroform-methanol mixture (2:1) for 3-4 hours.
  6. Filter and collect the filtrate.
  7. Evaporate extract to dryness.
  8. Dissolve residue in petroleum ether and re-precipitate with cold acetone.
  9. Dry under vacuum and store in chloroform-methanol or as solid.
• What materials, reagents, and equipment are needed for qualitative tests for lipids?

  • Test tubes
  • Test tube holder
  • Test tube rack
  • Bunsen burner
  • Dropper
  • Filter paper
  • Light source
  • Clarified butter
  • Potassium bisulphate
  • Cholesterol
  • Chloroform
  • Acetic anhydride
  • Concentrated sulfuric acid
  • Oleic acid
  • Petroleum ether
  • Copper acetate solution
  • Various oils (vegetable, linseed, olive, sunflower, palm, corn, coconut)
• What are the steps for the Acrolein test?

  1. Label 3 test tubes with clarified butter, vegetable oil, and linseed oil.
  2. Add 2ml of each to their respective tubes.
  3. Add potassium bisulphate crystals to each tube.
  4. Heat the mixture directly on a burner.
  5. Observe gas formation and odor.
  6. Record observations.
• What are the steps for the Liebermann-Burchard test?

  1. Dissolve 2ml of cholesterol in chloroform in a test tube.
  2. Add 2ml of acetic anhydride and mix.
  3. Add 5 drops of concentrated sulfuric acid and gently mix.
  4. Observe for a bluish-green color.
  5. Record observations.
• What are the steps for the Copper Acetate test?

  1. Label 2 test tubes with olive and oleic acid.
  2. Add 2ml of each to their respective tubes.
  3. Add petroleum ether to both tubes.
  4. Shake to mix.
  5. Add copper acetate solution to both tubes.
  6. Shake vigorously.
  7. Observe for blue-green color.
  8. Record observations.
• What are the steps for the Spot/Translucent test?

  1. Prepare filter paper and drop clarified butter on it, pressing another paper on top.
  2. Hold against a light source.
  3. Repeat with vegetable oil and linseed oil.
  4. Record observations.
• What are the steps for the Test for Unsaturation?

  1. Label 5 test tubes with different oils.
  2. Add 1ml of each oil to their respective tubes.
  3. Add drops of bromine water to each tube.
  4. Shake each test tube vigorously.
  5. Note if the color of bromine water disappears.
  6. Record observations.
• What are the key points from the post-lab discussion on lipid extraction from egg yolk?

  • Phospholipids are insoluble in acetone; triglycerides and sterols are soluble.
  • Egg yolk is a source of lecithin, which is amphiphilic.
  • Lecithin can be extracted chemically or mechanically.
  • Sources include soybeans, eggs, milk, and others; it is an excellent emulsifier.
• What is the purpose of the Acrolein test?

  • To detect the presence of glycerol or fat.
  • Positive result: pungent smell indicates glycerol is present.
  • Negative result: no smell indicates glycerol is absent.
• What is the objective of the Liebermann-Burchard test?

  • To detect the presence of cholesterol.
  • Positive result: bluish-green color indicates cholesterol.
  • Negative result: no color change.
• What does the Copper Acetate test distinguish between?

  • Distinguishes between oils and fatty acids.
  • Unsaturated fatty acids react with copper acetate; oils do not.
  • Positive result: green color for unsaturated fatty acids.
  • Negative result: white-blue precipitate for saturated fatty acids.
• What is the principle of the Spot/Translucent test?

  • Preliminary test for lipids characterized by a translucent spot.
  • Lipids form a greasy spot on filter paper; water does not.
  • Positive result: translucent spot appears.
  • Negative result: no translucent spot.
• What is the purpose of the Test for Unsaturation?

  • To detect unsaturated fatty acids or double bonds in lipids.
  • Positive result: pink color disappears with unsaturated fatty acids.
  • Negative result: pink color remains.
• What is the role of lecithin in food processing?

  Lecithin is used for smoothing food textures, dissolving powders, emulsifying, and homogenizing mixtures
• What happens to glycerol when fat is treated with potassium bisulphate?

  Glycerol is dehydrated to form acrolein, an unsaturated aldehyde
• What indicates a positive result in the Acrolein test?

  A pungent smell indicates the presence of glycerol
• What indicates a positive result in the Liebermann-Burchard test?


  A bluish-green color indicates the presence of cholesterol
• What indicates a positive result in the Copper Acetate test?

  A blue-green color indicates the presence of unsaturated fatty acids
• What indicates a positive result in the Spot/Translucent test?

  A translucent spot appears on the filter paper
• What indicates a positive result in the Test for Unsaturation?

  The pink color of bromine water disappears