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General Properties of Lipids Naturally-occurring organic compounds that are: 1- insoluble in water 2- soluble in nonpolar organic solvents, such as diethyl ether, acetone, carbon tetrachloride. 3- Contain carbon, hydrogen, oxygen, sometimes contain nitrogen and phosphorus 2

4- Lipids can be extracted from cells and tissues by organic solvents. 5- They yield fatty acids on hydrolysis or combine with fatty acids to form esters. 6- The solubility property distinguishes lipids from the three other major classes of natural products —carbohydrates, proteins, and nucleic acids—which in general are not soluble in organic solvents. 3

Lipids include.. 1. Fats & Oils (Triglycerides) 2. Waxes: they are simple monoesters (acid & alcohol). 3. Steroids 4. Fat-soluble vitamins (A, D, E, K) 5. Monoglycerides 6. Diglycerides 7. Phospholipids 4

Fatty Acids 1.Straight-chain organic acids 2.Found in natural fats, usually contain an even number of carbon atoms. 3.Can be either saturated or unsaturated 4.Polyunsaturated fatty acids contain many double bonds. 5.Unsaturated fatty acids have a lower melting point than the corresponding saturated fatty acids. 6.The greater the degree of unsaturation, the lower the melting point. 5

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Some Common Fatty acids 7

Fatty Acid Composition of Some Fats and Oils 8

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Classification of Lipids Lipids can be classified into three classes: 1. Simple lipids 2. Complex lipids 3. Precursor & Derived lipids 10

1. Simple Lipids They are esters of fatty acids, upon hydrolysis they give fatty acids & alcohol: simple lipid hydrolysis Fatty acids + Alcohol If the result of hydrolysis is: 1. three fatty acids & glycerol (then it is fat or oil) 2. One fatty acid and high molecular mass monohydric alcohol (then it is wax such as carnauba, bees wax) 11

2. Complex Lipids Are lipids that give one or more fatty acids, an alcohol, and some other type of compounds. Complex lipids hydrolysis fatty acid + alcohol + other compounds Some examples of complex lipids: 1.Phospholipids 2.Glycolipids (cerebrosides) 3.Sulfolipids 4.Aminolipids 5.Lipoproteins 12

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3. Precursor & Derived Lipids 14

Fats & Oils 15

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Iodine Number 17

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Used of Fats in the body 19

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Physical Properties of Fats & Oils Pure fats are white, solid Pure oils are yellow, liquid. Odorless & tasteless, but over a period of time they become rancid. Insoluble in water Soluble in organic solvents such as benzene, acetone, ether. Fats do not diffuse through a membrane. Fats have a greasy feeling. 21

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Chemical Properties of Fats & Oils 23

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Hydrolysis:  When butter is let to stand at room temp. hydrolysis takes place between the fats and the water present in the butter.  The result of this hydrolysis is fatty acid and glycerol.  One of the products of the hydrolysis is butyric acid, responsible for the disagreeable odor.  Note: to avoid rancidity keep the butter covered in a cool place. 29

Oxidation:  Oxygen present in air oxidizes some unsaturated fatty acids of fats & oils.  If this oxidation produces a short chain acids or aldehydes, the fat turns rancid (as evidenced by a disagreeable odor and taste).  Oxidation of fats can be inhibited by the addition of antioxidants such as vitamin C & E. 30

How do Soaps work? Soaps are salts of fatty acids, produced by reacting of fats with strong bases. 2 Types of soaps: - Bar soap: NaOH is the base (solid soap) - Soft soap: KOH is the base (liquid soap) F. A + NaOH Sodium salt of F.A + H 2 O 31

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Prostaglandins, Leukotrienes, and Lipoxins Prostaglandins are a group of compounds related to the unsaturated fatty acids. On the assumption that these substances came from the prostate gland, they were named prostaglandins. We now know that prostaglandins are widely distributed in almost all human tissues, that they are biologically active in minute concentration, and that they have various effects on: - fat metabolism, - heart rate, - blood pressure. 34

Prostaglandins have excited much interest in the medical community, where they are used in the treatment of: - inflammatory diseases, such as asthma and rheumatoid arthritis; - treatment of peptic ulcers; - control of hypertension; - regulation of blood pressure - metabolism; - inducing of labor - therapeutic abortions. 35

Steroids Tetracyclic compounds with high molecular mass. Steroids containing 1 or more OH groups are called sterols. Most common sterol is cholesterol, found in animal fat. Most of body cholesterol is produced by liver Bile salts, sex hormones (testosterone & estrogen) are synthesized from cholesterol. 36

Anabolic Steroids Hormones that control the synthesis of larger molecules from smaller ones. Example of anabolic steroids: 1.Testosterone: it increases muscle mass  Side effects of anabolic hormones In men - Testicular atrophy - hypercholesterolemia - Breast growth - Liver cancer 37

In women - Increased masculinity - Formation of a greater body hair - Deepening of the voice - menstrual irregularities 38