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LIPIDS

LIPIDS. Dr. Noha Soliman. Definition. Lipids are complex molecules composed of carbon , hydrogen , and oxygen . Lipids are insoluble in water and soluble in nonpolar solvents. Most lipids are non-polar and are hydrophobic because they contain hydrocarbon chains.

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LIPIDS

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  1. LIPIDS Dr. NohaSoliman

  2. Definition • Lipids are complex molecules composed of carbon , hydrogen , and oxygen. • Lipids are insoluble in water and soluble in nonpolar solvents. • Most lipids are non-polar and are hydrophobic because they contain hydrocarbon chains.

  3. Functions of lipids • The Functions of Fat in the Body: • Energy source esp. for muscles. • Serves as an energy reserve. Lipid (TGL) Droplets In Adipose tissue

  4. 3. Cell Membrane Structural components 4. Cushion the vital organs to protect them from shock.

  5. 5. Thermal Insulator : Subcutaneous layer of fat reduces heat loss in cold weather (helps maintain body temperature).

  6. B. The Functions of Fat in Food: • Provide calories (9 kcal per gram). • Provide satiety. • Carry Lipid-soluble vitamins (A,D,E, and K)& essential fatty acids. • Contribute aroma & flavor.

  7. Human adipose cells swollen with fat!!!!! As we gain and lose weight, they just swell and shrink. Humans can grow more fat cells, but can never get rid of them!! …Makes you think twice about those French fries!!!

  8. Bad Things About Fat • Makes you fat! • Heart disease, high blood pressure, cancer.

  9. FATTY ACIDS • Are long-chain monocarboxylic acids. • Generally contain an even number of carbon atoms. • General formula is CH3 (CH2)n COOH.

  10. CLASSIFICATIONS OF FATTY ACID • Length of the Carbon Chain • Long-chain, medium-chain, short-chain • Degree of Unsaturation • Saturated, Unsaturated (Mono, Poly) • Location of Double Bonds • Omega-3 Fatty Acid, Omega-6 Fatty Acid

  11. The Length of the Carbon Chain Short-chain Fatty Acid (less than 6 carbons) Medium-chain Fatty Acid (6-10 carbons) Long-chain Fatty Acid (12 or more carbons)

  12. Fat Saturation Saturation means “full”, so what could they be full of? Full of Hatoms! And wherever there is a chemical bond, there is stored energy.

  13. Properties of saturated fatty acids • General Formula: CH3 (CH2)n COOH. • Each C being “saturated” with H. • Contain only single C–C bonds. • long, straight chain.

  14. Properties of saturated fatty acids • Closely packed. • Strong attractions between chains. • High melting points. • Solids at room temperature.

  15. Animal foods such as meat, poultry and full-fat dairy products. • Tropical oils such as palm and coconut.

  16. Contributes to cardiovascular disease. • (atherosclerosis)

  17. LAURIC ACID

  18. Properties of unsaturated fatty acids • Contain one or more double C=Cbonds. • The kinks made by double bonded C prevent the molecules from packing tightly together. • Few interactions between chains.

  19. Properties of unsaturated fatty acids • Low melting points • Liquids at room temperature • Plant & fish fats • Vegetable oils

  20. Saturated vs. unsaturated saturated unsaturated 

  21. Fatty acids may be further subdivided as follows: • Monounsaturated FA • Polyunsaturated FA • Eicosanoids

  22. Numbering & Nomenclature

  23. Fatty acids are named after corresponding hydrocarbons: • Carbon atoms are numbered from the carboxyl carbon (C1). • Carbon atom adjacent to C1 (C2) is α-carbon. • C3 and C4 are the β- and γ carbons. • Terminal carbon is ω-carbon or n-carbon.

  24. Monounsaturated Fatty Acids (MUFA) • Containing one double bond. Oleic (most common FA) 18:1;9

  25. Polyunsaturated Fatty Acids(PUFA) • Containing two or more double bonds Linoleic (corn, peanut, cottonseed) 18:2;9,12

  26. Polyunsaturated Fatty Acids • Are identified by position of the double bond nearest the methyl end (CH3) of the carbon chain; this is described as an omega number. • If PUFA has first double bond 3 carbons away from the methyl end = omega 3 FA • 6 carbons from methyl end = omega 6 FA

  27. ω3, ω6, ω9 Fatty Acids

  28. Indicating Number & Position of Double Bond 18:1,9 Δ9 18:1 ω9,C18:1

  29. Trans-Fatty Acid • H’s on the opposite side of the double bond; occur in partially hydrogenated food Cis-Fatty Acid H’s on same side of the double bond; fold into a U-like formation; naturally occurring

  30. Essential Fatty Acids • linoleic acid and linolenic acid are important for synthesizing arachidonic acid (20 C atoms) • Arachidonic acid in turn is the precursor for the synthesis ofeicosanoids • Prostaglandins • Leukotrienes • Thromboxanes Arachidonic acid

  31. CHEMICAL REACTIONS OF FATTY ACID • Esterification • Fatty acids react with alcohols to form esters and water • Acid Hydrolysis • Producing fatty acids from esters • Opposite of esterification

  32. Saponification: Alkaline hydrolysis produces glycerol and salts of fatty acids (soaps).

  33. Reaction at the Double Bond (Unsaturated Fatty Acids): • Hydrogenation • Used in the food industry to convert polyunsaturated vegetable oils into saturated solid fats. • Partial Hydrogenation • Carried out to add hydrogen to some, but not all, double bonds in polyunsaturated oils • In this way liquid vegetable oils are converted into solid form (Crisco and margarine)

  34. Classification of lipids Lipids 2. Complex Lipids 1. Simple Lipids 3.Precursor & Derived Lipids

  35. Simple lipids • Esters of fatty acids and alcohol. (trihydric or monohydric alcohol).

  36. FAT and OIL • Fats :esters of fatty acids with glycerol. • Ex. triglycerides. • Oils : are fats in liquid state.

  37. Triglycerides • Triglycerides are the main dietary fats in human body. • It is a naturally occurring ester of three fatty acids and glycerol that is the chief constituent of fats and oils. • Glycerol forms the “backbone” of the fat.

  38. FAT vs. OIL • Fat: • is solid at room temperature. • is prevalent in meats, whole milk, butter, and cheese. • Oil: • Contain high proportion of unsaturated fatty acids and saturated fatty acids. • is liquid at room temperature. • is prevalent in plants such as olive and safflower. corn oil contains 86% unsaturated fatty acids and 14% saturated fatty acids

  39. Waxes • Estersof long-chain fatty acids with higher molecular weight monohydric alcohols. • Has a weakly polar head group (ester linkage) and non-polar tails (hydrocarbon chain). • Fatty acids found in waxes are usually saturated ex. stearic acid. • Alcohols may be saturated or unsaturated and may include sterols ex. cholesterol.

  40. Complex lipids Esters of fatty acids with various alcohols along with an additional group. Simple lipid + Additional group = Complex Lipids a.Phospholipids: Glycerophospholipids , Sphingophospholipids. b. Glycolipids c. Other Complex Lipids: Lipoproteins ,aminolipids and sulfolipids.

  41. Phosphoglycerides (Phospholipids) • They are phosphate esters. • Structure: • glycerol + 2 fatty acids + PO4 + polar molecule ( x).

  42. Phospholipid Structure

  43. Phospholipids • It is an amphipathic molecule: • Fatty acid tails = hydrophobic • Polar region (glycerol + carbonyl o of fatty acids + PO4 + x)= hydrophilic • dual “personality” It likes water & also pushes it away! interaction with H2O is complex & very important!

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