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Lab (3) Molecular Cell Biology C- Lipids

Lab (3) Molecular Cell Biology C- Lipids. C- Lipids in cells & Tissues Objective: Identifying lipids in tissues. Lipids Definition : are macromolecules including many fatty substances and their derivatives.

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Lab (3) Molecular Cell Biology C- Lipids

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  1. Lab (3) Molecular Cell Biology C- Lipids

  2. C- Lipids in cells & Tissues Objective: Identifying lipids in tissues Lipids Definition : are macromolecules including many fatty substances and their derivatives. Lipid molecules composed of C, H and O, and other atoms as Phosphor. They are water-insoluble but dissolve in organic solvents as alcohol and acetone. Biological Significance of Lipids: 1- Component of cellular membranes. 2- Second source of energy (after carbohydrates) and contains more energy than carbohydrates. 3- Some hormones are lipid-derivatives. 4- Work as heat insulator, and shock absorber.

  3. Type of Lipids : are divided into 4 types: • 1- Neutral fats:Most lipids in cell and in general are neutral fats. They are composed of 1 molecule of glycerol and 3 molecules of fatty acids. Neutral fats can be either saturated fats like butter, or unsaturated like oils. • 2- Phospholipids: Has 1 phosphate group (PO4) instead of 1 fatty acid. Found in all cells as component of cellular membranes, e.g. Phospha-tidyl-choline , Sphingo-myelin , Phospha-tudyl-serine • 3- Steroids:differs from other lipids in that it contains a steroid nucleus (fat ring complex) (4 cyclic rings, 3 of which are 6 C and 1 is 5 C ring). e.g. sex hormones and cholesterol.

  4. 4- Waxes:similar to neutral fats structure but instead of glycerol they contains other larger alcohols.

  5. Chemical Experiments Objective: detection of lipid substances in samples (1) Detection of Cholesterol in samples: milk, butter, margarine, olive oil and corn oil 1- Mark 6 tubes from 1-6, to each tube add 0.5 ml of acidic potassium sulfate KHSO4. Add 5 drops of each sample to each tube, then add 2.5 ml of KHSO4 Heat over flame for few minutes. 2- Mark 6 new tubes from 1-6, to each tube add 2 ml of sample + 1 ml chloroform + 1 ml of acetic anhydride (CH3CO)2O + 2 ml of conc. Sulfuric acid (very carefully).

  6. Observation: With KHSO4 acidic potassium sulfate : sample containing cholesterol has distinctive odor. With (CH3CO)2O acetic anhydride : sample containing cholesterol develop dark colors varying from red to brown to black according to cholesterol concentration. Results:

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