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Main lecture for lipids


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Main lecture for lipids

  1. 1. Lipids <ul><li>Types of Lipids </li></ul><ul><li>Fatty Acids </li></ul><ul><li>Fats, and Oils </li></ul><ul><li>Chemical Properties of Triglycerides </li></ul>
  2. 2. Types of Lipids <ul><li>Lipids with fatty acids </li></ul><ul><li>Waxes </li></ul><ul><li>Fats and oils (trigycerides) </li></ul><ul><li>Phospholipids </li></ul><ul><li>Sphingolipids </li></ul><ul><li>Lipids without fatty acids </li></ul><ul><li>Steroids </li></ul>
  3. 3. Fatty Acids <ul><li>Long-chain carboxylic acids </li></ul><ul><li>Insoluble in water </li></ul><ul><li>Typically 12-18 carbon atoms (even number) </li></ul><ul><li>Some contain double bonds </li></ul><ul><li>corn oil contains 86% unsaturated fatty acids and 14% saturated fatty acids </li></ul>
  4. 4. Saturated and Unsaturated Fatty Acids <ul><li>Saturated = C–C bonds </li></ul><ul><li>Unsaturated = one or more C=C bonds </li></ul>
  5. 5. Structures <ul><li>Saturated fatty acids </li></ul><ul><li>Fit closely in regular pattern </li></ul><ul><li>Unsaturated fatty acids </li></ul><ul><li>Cis double bonds </li></ul>
  6. 6. Properties of Saturated Fatty Acids <ul><li>Contain only single C–C bonds </li></ul><ul><li>Closely packed </li></ul><ul><li>Strong attractions between chains </li></ul><ul><li>High melting points </li></ul><ul><li>Solids at room temperature </li></ul>
  7. 7. Properties of Unsaturated Fatty Acids <ul><li>Contain one or more double C=C bonds </li></ul><ul><li>Nonlinear chains do not allow molecules to pack closely </li></ul><ul><li>Few interactions between chains </li></ul><ul><li>Low melting points </li></ul><ul><li>Liquids at room temperature </li></ul>
  8. 8. Learning Check L1 <ul><li>How would the melting point of stearic acid compare to the melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain. </li></ul><ul><li>stearic acid (18 C) saturated </li></ul><ul><li>oleic acid (18 C) one double bond </li></ul><ul><li>linoleic acid (18 C) two double bonds </li></ul>
  9. 9. Solution L1 <ul><li>Stearic acid is saturated and would have a higher melting point than the unsaturated fatty acids. Because linoleic has two double bonds, it would have a lower mp than oleic acid, which has one double bond. </li></ul><ul><ul><ul><li>stearic acid mp 69°C </li></ul></ul></ul><ul><ul><ul><li>oleic acid mp 13°C </li></ul></ul></ul><ul><li>linoleic acid mp -17°C </li></ul>
  10. 10. Fats and Oils <ul><li>Formed from glycerol and fatty acids </li></ul>
  11. 11. Triglycerides (triacylglcerols) <ul><li>Esters of glycerol and fatty acids </li></ul>
  12. 12. Learning Check L2 <ul><li>What are the fatty acids in the following triglyceride? </li></ul>
  13. 13. Solutions L2 <ul><li>What are the fatty acids in the following triglyceride? </li></ul>Stearic acid Oleic acid Myristic acid
  14. 14. Properties of Triglycerides <ul><li>Hydrogenation </li></ul><ul><li>Unsaturated compounds react with H 2 </li></ul><ul><li>Ni or Pt catalyst </li></ul><ul><li>C=C bonds C–C bonds </li></ul><ul><li>Hydrolysis </li></ul><ul><li>Split by water and acid or enzyme catalyst </li></ul><ul><li>Produce glycerol and 3 fatty acids </li></ul>
  15. 15. Hydrogenation
  16. 16. Product of Hydrogenation <ul><li>Hydrogenation converts double bonds in oils to single bonds. The solid products are used to make margarine and other hydrogenated items . </li></ul>
  17. 17. Hydrolysis <ul><li>Triglycerides split into glycerol and three fatty acids (H + or enzyme catalyst) </li></ul>
  18. 18. Saponification and Soap <ul><li>Hydrolysis with a strong base </li></ul><ul><li>Triglycerides split into glycerol and the salts of fatty acids </li></ul><ul><li>The salts of fatty acids are “soaps” </li></ul><ul><li>KOH gives softer soaps </li></ul>
  19. 19. Saponification
  20. 20. Learning Check L3 <ul><li>What are the products obtained from the complete hydrogenation of glyceryl trioleate? </li></ul><ul><li>(1) Glycerol and 3 oleic acids </li></ul><ul><li>(2) Glyceryltristearate </li></ul><ul><li>(3) Glycerol and 3 stearic acids </li></ul>
  21. 21. Solution L3 <ul><li>What are the products obtained from the complete hydrogenation of glyceryl trioleate? </li></ul><ul><li>2. Glyceryltristearate </li></ul>
  22. 22. The Lipids: Triglycerides, Phospholipids and Sterols
  23. 23. Lipids Objectives <ul><li>1. Understand the chemical composition and differences between fats </li></ul><ul><li>2. Explain the structural and functional processes of triglycerides, phospholipids, and sterols </li></ul><ul><li>3. Describe the process of fat digestion and absorption </li></ul><ul><li>4. Discuss the different types of lipoproteins in the body </li></ul><ul><li>5. Clarify the recommended intakes of fat and essential fatty acid requirements to meet daily nutritive needs </li></ul><ul><li>6. Describe the health-risk factors with over consumption of lipids in the diet </li></ul>
  24. 24. Fatty Acids <ul><li>The Length of the Carbon Chain </li></ul><ul><ul><li>long-chain, medium-chain, short-chain </li></ul></ul><ul><li>The Degree of Unsaturation </li></ul><ul><ul><li>saturated, unsaturated, monounsaturated, polyunsaturated </li></ul></ul><ul><li>The Location of Double Bonds </li></ul><ul><ul><li>omega-3 fatty acid, omega-6 fatty acid </li></ul></ul>
  25. 25. 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)
  26. 26. Fatty Acids are Key Building Blocks <ul><li>Saturated Fatty Acid </li></ul><ul><ul><ul><li>All single bonds between carbons </li></ul></ul></ul>
  27. 27. Monounsaturated Fatty Acid (MUFA) <ul><ul><li>One carbon-carbon double bond </li></ul></ul>
  28. 28. Polyunsaturated Fatty Acid (PUFA) <ul><ul><li>More than one carbon-carbon double bond </li></ul></ul>
  29. 29. Location of Double Bonds <ul><li>PUFA are identified by position of the double bond nearest the methyl end (CH 3 ) of the carbon chain; this is described as a omega number; </li></ul><ul><li>If PUFA has first double bond 3 carbons away from the methyl end=omega 3 FA </li></ul><ul><li>6 carbons from methyl end=omega 6 FA </li></ul>
  30. 30. Degree of Unsaturation <ul><li>Firmness </li></ul><ul><ul><li>saturated vs. unsaturated </li></ul></ul><ul><li>Stability </li></ul><ul><ul><li>oxidation, antioxidants </li></ul></ul><ul><li>Hydrogenation </li></ul><ul><ul><li>advantages, disadvantages </li></ul></ul><ul><li>Trans-Fatty Acids </li></ul><ul><ul><li>from hydrogenation </li></ul></ul>
  31. 31. Hydrogenation
  32. 32. Cis-fatty acid : H’s on same side of the double bond; fold into a U-like formation; naturally occurring; Trans-fatty acid : H’s on opposite side of double bond; more linear; occur in partially hydrogenated foods;
  33. 35. 1. Shortening 2. Cube margarine: vegetable oil blend (partially hydrogenated soybean oil and liquid soybean oil), water, whey, etc 1 Tbsp: 9 g fat; 2 g SFA; 2 g PUFA; 2.5 g MUFA; 3. Light Tub Margarine: water, liquid and partially hydro- genated soybean oil, maltodextrin, etc. 1 Tbsp: 6 g fat; 1 g SFA;
  34. 36. Trans-fat must be listed on Food Label By January 1, 2006
  35. 39. But, is all Trans Fat Bad? CLA Conjugated Linoleic Acid
  36. 40. Essential Fatty Acids (EFA) <ul><li>Omega-3: </li></ul><ul><ul><li>Eicosopentaenoic acid (EPA) </li></ul></ul><ul><ul><li>Docosahexaenoic acid (DHA) </li></ul></ul><ul><ul><li>Alpha-linolenic acid (ALA) </li></ul></ul><ul><ul><ul><li>flaxseed--most, canola (rapeseed), soybean, walnut, wheat germ </li></ul></ul></ul><ul><ul><ul><li>body can make some EPA and DHA from ALA </li></ul></ul></ul><ul><li>Omega-6 </li></ul><ul><ul><li>corn, safflower, cottonseed, sesame, sunflower </li></ul></ul><ul><ul><li>Linoleic acid </li></ul></ul>FISH
  37. 41. Omega-3 Omega-6
  38. 42. Omega-3 Fatty Acids <ul><li>Associated with: </li></ul><ul><ul><li>anti-inflammatory, antithrombotic, antiarrhythmic, hypolipidemic, vasodilatory properties </li></ul></ul><ul><li>Inflammatory conditions </li></ul><ul><li>Ulcerative colitis, Crohn’s </li></ul><ul><li>Cardiovascular disease </li></ul><ul><li>Type 2 diabetes * Mental function </li></ul><ul><li>Renal disease * Growth and development </li></ul>
  39. 43. Essential Fatty Acid Deficiency <ul><li>Classical symptoms include: </li></ul><ul><ul><li>growth retardation, reproductive failure, skin lesions, kidney and liver disorders, subtle neurological and visual problems </li></ul></ul><ul><li>People with chronic intestinal diseases </li></ul><ul><li>Depression--omega-3 </li></ul><ul><ul><li>?inadequate intake alters brain activity or depression alters fatty acid metabolism? </li></ul></ul><ul><li>Attention Deficit Hyperactivity Disorder </li></ul><ul><ul><li>lower levels of omega-3--more behavioral problems </li></ul></ul>
  40. 44. Eicosanoids: made from EFA --derivatives of 20-carbon fatty acids; --affect cells where they are made; --have different effects in different cells --cause muscles to contract and muscles to relax; -- help regulate blood pressure, blood clot formation, blood lipids, and immune response; --participate in immune response to injury and infection, producing fever, inflammation, and pain; --include:prostaglandins, thromboxanes, leukotrienes
  41. 45. Triglycerides <ul><li>Structure </li></ul><ul><ul><li>Glycerol + 3 fatty acids </li></ul></ul><ul><li>Functions </li></ul><ul><ul><li>Energy source </li></ul></ul><ul><ul><ul><li>9 kcals per gram </li></ul></ul></ul><ul><ul><ul><li>Form of stored energy in adipose tissue </li></ul></ul></ul><ul><ul><li>Insulation and protection </li></ul></ul><ul><ul><li>Carrier of fat-soluble vitamins </li></ul></ul><ul><ul><li>Sensory properties in food </li></ul></ul>
  42. 46. Triglycerides : lipids composed of three fatty acids attached to a glycerol
  43. 47. Triglycerides <ul><li>Food sources </li></ul><ul><ul><li>fats and oils </li></ul></ul><ul><ul><ul><li>butter, margarine, meat, baked goods, snack foods, salad dressings, dairy products, nuts, seeds </li></ul></ul></ul><ul><ul><li>Sources of omega-3 fatty acids </li></ul></ul><ul><ul><ul><li>Soybean, canola, walnut, flaxseed oils </li></ul></ul></ul><ul><ul><ul><li>Salmon, tuna, mackerel </li></ul></ul></ul><ul><ul><li>Sources of omega-6 fatty acids </li></ul></ul><ul><ul><ul><li>Vegetable oils </li></ul></ul></ul>
  44. 48. Fatty Acids in Common Food Fats
  45. 50. Phospholipids <ul><li>Structure </li></ul><ul><ul><li>Glycerol + 2 fatty acids + phosphate group </li></ul></ul><ul><li>Functions </li></ul><ul><ul><li>Component of cell membranes </li></ul></ul><ul><ul><li>Lipid transport as part of lipoproteins </li></ul></ul><ul><ul><li>Emulsifiers </li></ul></ul><ul><ul><li>Phosphatidylcholine </li></ul></ul><ul><li>Food sources </li></ul><ul><ul><li>Egg yolks, liver, soybeans, peanuts </li></ul></ul>
  46. 51. Cell membranes are phospholipid bilayers
  47. 53. Sterols: Cholesterol <ul><li>Functions </li></ul><ul><ul><li>Component of cell membranes </li></ul></ul><ul><ul><li>Precursor to other substances </li></ul></ul><ul><ul><ul><li>Sterol hormones </li></ul></ul></ul><ul><ul><ul><li>Vitamin D </li></ul></ul></ul><ul><ul><ul><li>Bile acids </li></ul></ul></ul><ul><li>Synthesis </li></ul><ul><ul><li>Made mainly in the liver </li></ul></ul><ul><li>Food sources </li></ul><ul><ul><li>Found only in animal foods </li></ul></ul>
  48. 54. Lipid Digestion <ul><li>In the Mouth </li></ul><ul><ul><li>hard fats begin to melt; lingual lipase </li></ul></ul><ul><li>In the Stomach </li></ul><ul><ul><li>gastric lipase--SCFA </li></ul></ul><ul><li>In the Small Intestine </li></ul><ul><ul><li>release of CCK; bile-emulsifier; fat drawn into surrounding watery fluids; intestinal lipases; remove each TG fatty acid; leave glycerol; </li></ul></ul><ul><li>Bile Routes </li></ul><ul><ul><li>reabsorbed or trapped by dietary fiber </li></ul></ul>
  49. 56. <ul><li>Olestra </li></ul><ul><ul><ul><li>Sucrose + fatty acids </li></ul></ul></ul><ul><ul><ul><li>Indigestible – provides zero kcals </li></ul></ul></ul><ul><ul><ul><li>Reduces absorption of fat-soluble vitamins </li></ul></ul></ul><ul><ul><ul><li>So many fatty acid chains are crowded around the core, the digestive enzymes cannot find a breaking point </li></ul></ul></ul><ul><li>Orlistat (Xenical) </li></ul><ul><li>* binds to active site of GI lipase and blocks its activity; thus, lipase can’t break TG down to component parts; TG remains undigested and unabsorbed </li></ul>
  50. 57. Metabolic Pathways and Energy Production <ul><li>Metabolism and ATP Energy </li></ul><ul><li>Important Coenzymes </li></ul><ul><li>Glycolysis </li></ul>
  51. 58. Metabolism <ul><li>All the chemical reactions that occur in the cells of our bodies. </li></ul><ul><li>Catabolic reactions </li></ul><ul><li>Break down large molecules </li></ul><ul><li>Provide energy for ATP </li></ul><ul><li>Anabolic reactions </li></ul><ul><li>Use small molecules to build large ones </li></ul><ul><li>Require energy </li></ul>catabolic anabolic
  52. 59. Cell Structure <ul><li>Typical animal cell </li></ul><ul><li>Nucleus </li></ul><ul><li>Chromosomes in the nucleus contain genetic material </li></ul><ul><li>Cytoplasm is material between nucleus and cell membrane </li></ul><ul><li>Mitochondria are where energy-producing reactions occur </li></ul>
  53. 60. ATP <ul><li>Energy is released as food is oxidized </li></ul><ul><li>Used to form ATP from ADP and P i </li></ul><ul><li>ADP + P i + Energy ATP </li></ul><ul><li>In cells, energy is provided by the hydrolysis of ATP </li></ul><ul><li>ATP ADP + P i + Energy </li></ul>
  54. 61. Structure of ATP
  55. 62. Digestion of Foods <ul><li>Digestion is the first step of catabolism </li></ul><ul><li>Carbohydrates glucose, fructose, galactose </li></ul><ul><li>Proteins amino acids </li></ul><ul><li>Lipids glycerol </li></ul><ul><li>fatty acids </li></ul>
  56. 63. Coenzymes <ul><li>Substances that connect metabolic pathways </li></ul><ul><li>In reduction, coenzymes accept H atoms </li></ul><ul><li>In oxidation, coenzymes remove H atoms </li></ul><ul><li>FAD (flavin adenine dinucleotide) </li></ul><ul><li>FAD + -CH 2 -CH 2 - FADH 2 + -CH=CH- </li></ul><ul><li>NAD + (nicotinamide adenine dinucleotide) </li></ul><ul><li>NAD + + -CH-OH NADH + H + + -C=O </li></ul>
  57. 64. Glycolysis: Oxidation of Glucose <ul><li>2ATP </li></ul><ul><li>2 NAD + </li></ul><ul><li>2ADP 2NADH + 2H + </li></ul><ul><li>4 ADP </li></ul><ul><li>4 ATP </li></ul>Glucose two Glyceraldehyde-3-PO 4 two Pyruvate
  58. 65. Glycolysis: Oxidation of Glucose
  59. 66. Glycolysis: Oxidation of Glucose <ul><li> 2 NAD + 2 NADH + 2 H + </li></ul>
  60. 67. Glycolysis: Oxidation of Glucose <ul><li>Glycolysis generates </li></ul><ul><li> 2 ATP molecules and 2 NADH + 2 H + </li></ul><ul><li>Two ATP used in adding phosphate groups to glucose and fructose-6-phosphate (- 2 ATP) </li></ul><ul><li>Four ATP generated in direct transfer to ADP by two 3-C molecules (+ 4 ATP) </li></ul><ul><li>Glucose + 2 ADP + 2 P i + 2 NAD + </li></ul><ul><li>2pyruvate + 2 ATP + 2 NADH + 2 H + </li></ul>
  61. 68. Pathways for Pyruvate <ul><li>Aerobic conditions </li></ul><ul><li> O </li></ul><ul><li>|| </li></ul><ul><li>CH 3 –C –COO - + NAD + + CoA </li></ul><ul><li>pyruvate </li></ul><ul><li>O </li></ul><ul><li> || </li></ul><ul><li>CH 3 –C –CoA + CO 2 + NADH + H + </li></ul><ul><li>acetyl CoA </li></ul>
  62. 69. Pathways for Pyruvate <ul><li>Anaerobic conditions (No O 2 available) </li></ul><ul><li>Reduce to lactate to replenish NAD + for glycolysis </li></ul><ul><li>O OH </li></ul><ul><li>|| | </li></ul><ul><li>CH 3 –C –COO - + NADH + H + CH 3 –CH –COO - + NAD + </li></ul><ul><li>pyruvate lactate </li></ul><ul><li>enzyme: lactate dehydrogenase </li></ul>
  63. 70. Lactate in Muscles <ul><li>Strenuous exercise leads to anaerobic conditions </li></ul><ul><li>Oxygen in muscles is depleted </li></ul><ul><li>Lactate builds up as glycolysis continues </li></ul><ul><li>Muscles tire and become painful </li></ul><ul><li>Breathing rate increases </li></ul><ul><li>Rest repays oxygen debt </li></ul><ul><li>Lactate re-forms pyruvate in liver </li></ul>
  64. 71. Learning Check M1 <ul><li>Match the following with the terms below: </li></ul><ul><li>(1) Catabolic reactions (2) Coenzymes </li></ul><ul><li>(3) Glycolysis (4) Lactate </li></ul><ul><li>A. Produced during anaerobic conditions </li></ul><ul><li>B. Reactions that convert glucose to pyruvate </li></ul><ul><li>C. Metabolic reactions that break down large molecules to smaller molecules + energy </li></ul><ul><li>D. Substances that remove or add H atoms in oxidation and reduction reactions </li></ul>
  65. 72. Solution M1 <ul><li>Match the following with the terms below: </li></ul><ul><li>(1) Catabolic reactions (2) Coenzymes </li></ul><ul><li>Glycolysis (4) Lactate </li></ul><ul><li>A. 4 Produced during anaerobic conditions </li></ul><ul><li>B. 3 Reactions that convert glucose to pyruvate </li></ul><ul><li>C. 1 Metabolic reactions that break down large </li></ul><ul><li> molecules to smaller molecules + energy </li></ul><ul><li>D. 2 Substances that remove or add H atoms in </li></ul><ul><li>oxidation and reduction reactions </li></ul>