Chem 1152: Ch. 18 Lipids. Lipids Biomolecules defined in terms of solubility: –...

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Transcript of Chem 1152: Ch. 18 Lipids. Lipids Biomolecules defined in terms of solubility: –...

  • Slide 1
  • Chem 1152: Ch. 18 Lipids
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  • Lipids Biomolecules defined in terms of solubility: Insoluble in water but soluble in nonpolar solvents. Waxy, greasy or oily compounds. Biological Functions: Energy Storage Structural component of cell membranes Signaling molecules Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Two major classes
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  • Saponifiable Lipids Saponification: base hydrolysis of esters to produce carboxylic acid salt and alcohol Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Simple Lipids: Contain fatty acids and alcohols Complex Lipids: Contain multiple fatty acids, alcohol, something else
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  • Fatty Acids Building blocks of many lipids Long chain carboxylic acids Carboxyl group hydrophilic at physiological pH (7.4) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011
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  • Micelles In aqueous solutions, ionized fatty acids form spherical clusters Polar head is facing out towards water (hydrophilic) Long alkane chains associate in interior (hydrophobic) through weak dispersion forces Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011
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  • Characteristics of Fatty Acids 1.Straight chain (unbranched) carboxylic acids 2.Comprised of 10-20 carbons 3.Usually have even number of carbons 4.Can be saturated or unsaturated 5.Usually no other functional groups Unsaturated fatty acids usually contain double bonds in the cis configuration This creates kink or bend in chain that prevents unsaturated fatty acids from packing together closely unlike saturated fatty acids Results in weaker intermolecular forces, lower MPs Usually liquid at room temp unsaturated saturated Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011
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  • Properties of Unsaturated Fatty Acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 The kink or bend in chain of unsaturated fatty acids prevents from packing together closely unlike saturated fatty acids Results in weaker intermolecular forces, lower MPs Increases fluidity of biological membranes
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  • Properties of Unsaturated Fatty Acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Phospholipids form bilayer in cell membrane
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  • Essential Fatty Acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 The human body can synthesize all but two of the necessary fatty acids Linoleic acid (omega-6 fatty acid) Linolenic acid (omega-3 fatty acid) Must be obtained from diet (plant and fish oils) Polyunsaturated (multiple double bonds) 18 Carbons in chain Diets rich in omega-3 fatty acids may: decrease serum cholesterol, triglycerides reduce risk of heart disease Fish Nuts Kidney Beans Sources of omega-3 fatty acids: Spinach Broccoli and cauliflower Oils
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  • Structures of Fats and Oils Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Fats: Triglycerides from animal (saturated) Oils: Triglycerides from vegetables (unsaturated) These are esters (alcohol + acid) Alcohol derived from glycerol Acid from fatty acids Most common lipids triglyceride
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  • Reactions of Triglycerides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 hydrolysis saponification hydrogenation triglyceride Ester of 3 alcohols, 3 acids
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  • Chemical Properties of Fats and Oils Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Triglycerides exhibit chemical properties of esters and alkenes Rxn: Hydrolysis Breakdown of cellular fats to supply energy begins with lipase catalyzed hydrolysis reaction
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  • Chemical Properties of Fats and Oils Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Rxn: Saponification Soapmaking (up to AD 500), by adding base (lye or aqueous extract of wood ash) to animal fat
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  • Chemical Properties of Fats and Oils Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Rxn: Hydrogenation Results in partial hydrogenation (partially-hydrogenated vegetable oils) Semi-solids that dont separate Crisco
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  • Waxes Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Simple, saponifiable lipids (long chain fatty acid + alcohol = ester) Alcohol derived from long chain alcohols (12-32 carbons) not glycerols Water insoluble Occur in nature as protective coatings on: Feathers Fur Skin Leaves Fruits Beeswax
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  • Phosphoglycerides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Complex lipids Serve as major components of cell membranes Also known as phospholipids Structure similar to triglycerides triglyceride phosphoglyceride
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  • Phosphoglycerides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 The most common phosphoglycerides have choline, ehanolamine, or serine attached to the phosphate group.
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  • Phosphoglycerides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Lecithins Phospholglycerides that contain choline Soy lecithin used to provide smooth texture to margarine, chocolate Cephalins Phospholglycerides that contain ethanolamine or serine Functions: structural components of cell membranes micelle forming agents Functions: Cell membranes Blood-clotting Phosphatidylcholine (lecithin)Cephalin
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  • Sphingolipids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Complex lipid found in cell membrane Contain sphingosine instead of glycerol These are found in brain and nerve tissue, and in myelin sheath that surrounds nerves
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  • Glycolipids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Another type sphingolipid Contain carbohydrates AKA cerebrosides due to abundance in brain tissue No phosphate linkage
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  • Related Diseases Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Some human diseases are related to abnormal accumulation of sphingomyelins and glycolipids
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  • Fluid-mosaic Model of Biological Membranes Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Cell membranes for both prokaryotic and eukaryotic cells comprised of lipids organized in a bilayer
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  • Steroids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Exhibit feature of other lipids (e.g., soluble in non-polar solvents) Cholesterol is most abundant steroid in human body Essential component of cell membranes Precursor for other steroids: Bile salts Sex hormones Vitamin D Adrenocorticoid hormones Synthesized in liver or obtained from food May contribute to atherosclerosis SteroidCholesterol
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  • Bile Salts Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011; http://www.medicinenet.com/gallstones/article.htm Yellow-brown or green liver secretion stored in gallbladder Bile salts are released into intestine to separate large globules of lipids into smaller droplets Bile salts also emulsify (mix immiscibles) cholesterol found in the bile for excretion Gallstones may occur if cholesterol too high and/or bile salts too low
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  • Steroid Hormones http://schoolworkhelper.net/2010/07/the-endocrine-system-function-and-structure/ Hormone: Chemical produced in the cell or gland that delivers a message affecting cells in another part of the organism Steroid hormones derived from cholesterol Two Major Steroid Hormones: Adrenocorticoid Hormones Male and Female Sex Hormones Steroid hormones diffuse through the cell membrane and combine with receptor proteins in the cytoplasm Hormone-receptor complex cause cell to respond to hormone by interacting with cell DNA and stimulating protein synthesis
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  • Adrenocorticoid Hormones Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Produced in adrenal glands located at top of kidneys Classified into 2 functional groups: Mineralocorticoids: Regulate concentration of ions (Na+) in body fluids Aldosterone: most important mineralocorticoid Promotes absorption of Na + and Cl - in kidney tubules Glucorticoids: Enhance carbohydrate metabolism Cortisol is major glucocorticoid in human body Increases glucose and glycogen concentration in body Cortisol, cortisone and prednisolone exert anti-inflammatory effects Used to treat rheumatoid arthritis, bronchial asthma
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  • Male Sex Hormones Seager SL, Slabaug