Biochemistry Lab - 07 Properties of Lipids

BIOCHEMISTRY LABORATORY MODULE 7 - PROPERTIES OF LIPIDS BASIC REACTIONS OF LIPIDS • LIPIDS • • • Includes true fats and fat-like substance Another type of Organic Molecule for it contains Carbon Examples of Lipids o Waxes - Honeycombs, Ear wax, Cutin ▪ Cutin - waxy covering in plants o Steroids - Hormones ▪ end in -ol and -one o Fats - Triglycerides ▪ Triglycerides - most common fat in the body ▪ Energy reserve o Most lipid hormones are steroid hormones, which are usually ketones or alcohols and are insoluble in water. Steroid hormones (ending in '-ol' or '-one') include estradiol, testosterone, aldosterone, and cortisol o Triglycerides are a type of fat (lipid) found in your blood. When you eat, your body converts any calories it doesn't need to use right away into triglycerides. The triglycerides are stored in your fat cells. La CLASSIFICATION OF LIPIDS • • • True/ Neutral/Simple Lipids o are esters of the trihydroxy alcohol, glycerol, & high MW acid of the continuous chain type. o Designated as triglycerides or glyceryl esters o Glyceryl esters = glycerol + fatty acids Miscellaneous Lipids o Do not have the fatty acid radical o Same solubility property as fats o E.g. ADEK (fat soluble vitamins); sterols, carotenoids ▪ A - retinol/retinoic acid; for eyes & skin; keratogenic which is not suitable for pregnant ▪ D - cholecalciferol; for skin, bone formation (absorption of Ca, P, Mg) ▪ E - tocopherol; antioxidant eliminate free radicals ▪ K - phytomenadione; clot formation ▪ Sterols - cholesterol ▪ Carotenoids - pigment Compound Lipids o Those with phosphoric acid called Phosphatides o Those with nitrogenous bases as well as phosphoric acid called Phospholipids o Those with CHO called Glycolipids o Those with protein called Lipoprotein • • • • • SOLUBILITY OF LIPIDS • • • • Unsaturated Fatty Acid o mostly liquid or commonly as OILS o Double bond, Good cholesterol, high in anti-oxidant o HDL - good fats Saturated Fatty Acid o esters are solid o Single bond, bad cholesterol that can cause atherosclerosis (hardening of the arteries due to fat deposits) Note = fats and oils found in nature are usually both saturated and unsaturated Lipids - water insoluble organic substances found in cell. Lipids are soluble in non-polar solvents such as ether, CHCl3 (chloroform), & C6H6 (benzene) EXPERIMENT (ANALYSIS OF LIPIDS) • • FATS • Hydrolysis & Oxidation - the 2 most common reaction undergone by lipids o Hydrolysis - hydro (water) + lysis (unbind/break) Halogenation Reaction - with Br2 & I2 are tests for the degree of unsaturation of simple lipids o Addition of halogen (group 7 - I, Br, Cl, F) Hydrolysis reaction o LIPID + dilute acid (5% HCl) → (hydrolysis) glycerol + fatty acid o LIPID + dilute base (5% NaOH) → (hydrolysis) metallic salt of fatty acid o LIPOLYTIC ENZYME (body-lipase) → hydrolysis during digestion fatty acid + glycerol + glyceride o LIPID/OIL → DEHYDRATION →glycerol + acrolein/propenal (pungent odor) o Pungent - ammoniacal Oxidation reaction o UNSATURATED FATTY ACID → upon exposure to air>> RANCID ODOR/TASTE o RANCIDITY due to volatile fatty acid OXIDIZED to form rancid volatile aldehydes & ketones. This process destroys Carotene, Vitamin E & A o Rancid - old oil odor Distinct GLYCEROL smell with all six (butter, lard, Margarine, corn oil & tallow) bec. o Fats are triesters of Trihydroxy Alcohol, Glycerol & 3 Molecules of Fatty Acid– Separates Glycerol From Fatty Acid 2 Classifications of Lipids o Saponifiable ▪ yields fatty acid & alcohol on HYDROLYSIS ▪ Waxes triglyceride phospoglyceride, spingolipids o Non-Saponifiable ▪ does not yield these substances after hydrolysis ▪ Steroids and postalglandin • Test Samples o Cholesterol, Glycerine, Lecithin, Corn oil, Butter, Egg yolk, Margarine, Lanolin Phosphate Test (molybdate test) o detect the presence of phosphate in the hydrolysate by appearance of a purple color o it differentiates fat and cholesterol (negative) and phospholipid (positive) Acrolein Test o When Lipids Containing glycerol are heated in the presence of KHSO4, the glycerol is dehydrated, forming acrolein, which has an unpleasant acrid odor and causes tearing o further heating results in polymerization of acrolein (slight blackening of the reaction mixture) o both the pungent smell and the black color indicate the presence of glycerol (fat and/or lecithin) o this test can differentiate lecithin from cholesterol • Liebermann-Burchard Test o uses acetic anhydride and sulfuric acid as reagents, that gives a characteristic green color in the presence of cholesterol o due to the –OH group of cholesterol and the unsaturation found in the adjacent fused ring o the color change is gradual: pink to lilac to deep green