Chapter5

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  • Figure 5-12 Emulsification of Fat by Bile Like bile, detergents are emulsifiers and work the same way, which is why they are effective in removing grease spots from clothes. Molecule by molecule, the grease is dissolved out of the spot and suspended in the water, where it can be rinsed away.
  • Figure 5-14 Enterohepatic Circulation Most of the bile released into the small intestine is reabsorbed and sent back to the liver to be reused. This cycle is called the enterohepatic circulation of bile. Some bile is excreted.
  • Chapter5

    1. 1. The Lipids:The Lipids: Triglycerides,Triglycerides, Phospholipids, andPhospholipids, and SterolsSterols Chapter 5Chapter 5
    2. 2. IntroductionIntroduction • Poor health • Too much fat • Too little fat • Too much of some kinds of fat • Family of lipids • Triglycerides • Phospholipids • Sterols
    3. 3. ChemistChemist’s View of Fatty Acids’s View of Fatty Acids and Triglyceridesand Triglycerides • Energy provided per gram • More carbons and hydrogens • Preview of lipids • Triglycerides: glycerol and 3 fatty acids • Fatty acids: even number of carbons • Fatty acids: saturated or unsaturated • Omega-3 and omega-6 fatty acids • 18-carbon polyunsaturated fatty acids
    4. 4. ChemistChemist’s View of Fatty Acids’s View of Fatty Acids and Triglyceridesand Triglycerides • Fatty acids • Methyl group at one end; acid group at other end • Usually even number of carbons • 18-carbon fatty acids abundant in food • Saturations • Saturated – full of hydrogens • Unsaturated – missing hydrogens
    5. 5. 18-Carbon Fatty Acids
    6. 6. ChemistChemist’s View of Fatty Acids’s View of Fatty Acids and Triglyceridesand Triglycerides • Fatty acids • Location of double bonds • Nearest the methyl end of the carbon chain • Omega number • Linolenic acid • Monounsaturated fatty acids • Omega-9 groups
    7. 7. Omega-3 and Omega-6 Fatty Acids Compared
    8. 8. ChemistChemist’s View of Fatty Acids’s View of Fatty Acids and Triglyceridesand Triglycerides • Triglycerides • Glycerol backbone • Three fatty acids • Formed via series of condensation reactions • Usually contain mixture of fatty acids
    9. 9. Condensation of Glycerol andCondensation of Glycerol and Fatty Acids to Form a TriglycerideFatty Acids to Form a Triglyceride
    10. 10. ChemistChemist’s View of Fatty Acids’s View of Fatty Acids and Triglyceridesand Triglycerides • Characteristics of solid fats and oils • Firmness • Polyunsaturated fats • Saturated fats • Length of carbon chain • Stability • Oxidation and spoilage of fats
    11. 11. Diagram of Saturated & Unsaturated Fatty Acids Compared
    12. 12. Fatty Acid Composition of Common Food Fats
    13. 13. ChemistChemist’s View of Fatty Acids’s View of Fatty Acids and Triglyceridesand Triglycerides • Characteristics of solid fats and oils • Hydrogenation • Advantages • Trans-fatty acids • Configurations – cis and trans • Similarity to other types of fat
    14. 14. HydrogenationHydrogenation
    15. 15. Cis- andCis- and TransTrans-Fatty Acids-Fatty Acids ComparedCompared
    16. 16. ChemistChemist’s View of’s View of Phospholipids and SterolsPhospholipids and Sterols • Phospholipids • Solubility in fat and water • Emulsifiers in food industry • Lecithin • Food sources • Roles • Part of cell membranes • Emulsifiers
    17. 17. Lecithin
    18. 18. ChemistChemist’s View of’s View of Phospholipids and SterolsPhospholipids and Sterols • Sterols • Food sources • Cholesterol • Plant sterols • Roles of sterols • Body compounds made from cholesterol
    19. 19. Lipid DigestionLipid Digestion • Fats are hydrophobic • Digestive enzymes are hydrophilic • Goal of fat digestion • Dismantle triglycerides • Monoglycerides, fatty acids, and glycerol
    20. 20. Lipid DigestionLipid Digestion • Mouth • Lingual lipase • Stomach • Strong muscle contractions • Gastric lipase
    21. 21. Lipid DigestionLipid Digestion • Small intestine • Cholecystokinin (CCK) • Gall bladder releases bile • Bile acts as emulsifier • Pancreatic lipase • Hydrolysis • Triglycerides and phospholipids • Bile routes • Blood cholesterol levels
    22. 22. Fat Watery GI juices Fat In the stomach, the fat and watery GI juices tend to separate. The enzymes in the GI juices can’t get at the fat. When fat enters the small intestine, the gallbladder secretes bile. Bile has an affinity for both fat and water, so it can bring the fat into the water. Bile’s emulsifying action converts large fat globules into small droplets that repel each other. After emulsification, more fat is exposed to the enzymes, making fat digestion more efficient. Enzyme Bile Enzymes Stepped Art Emulsified fatEmulsified fat Figure 5-12 p140 Emulsified fat
    23. 23. Hydrolysis of a TriglycerideHydrolysis of a Triglyceride
    24. 24. Enterohepatic CirculationEnterohepatic Circulation
    25. 25. In the gallbladder, bile is stored. In the liver, bile is made from cholesterol. In the colon, bile that has been trapped by soluble fibers is lost in feces. In the small intestine, bile emulsifies fats. Stepped Art Figure 5-14 p141
    26. 26. Lipid AbsorptionLipid Absorption • Directly into bloodstream • Glycerol and short- & medium-chain fatty acids • Lymphatic system • Micelles diffuse into intestinal cells • Reassembly of triglycerides • Packed with proteins – chylomicrons • Bypass liver at first
    27. 27. Absorption of FatAbsorption of Fat
    28. 28. Lipid TransportLipid Transport • Four main types of lipoproteins • Chylomicrons • Largest and least dense • Transport diet-derived lipids • Liver removes remnants from blood • Very-low-density lipoproteins (VLDL) • Made in the liver • Proportion of lipid shift
    29. 29. Lipid TransportLipid Transport • Four main types of lipoproteins • Low-density lipoproteins (LDL) • Cell needs • Liver regulation • High-density lipoproteins (HDL) • Remove cholesterol from cells • Carry cholesterol to liver for recycling • Anti-inflammatory properties • Health implications
    30. 30. Sizes and Compositions of the Lipoproteins
    31. 31. Lipid Transport viaLipid Transport via LipoproteinsLipoproteins
    32. 32. Role of TriglyceridesRole of Triglycerides • Provide the cells with energy • Virtually unlimited ability to store fat energy in body • Adipose tissue • Secretes hormones • Adipokines • Skin insulation, shock absorption, cell membranes, and cell signaling pathways
    33. 33. An Adipose Cell
    34. 34. Essential Fatty Acids • Must be supplied by the diet • Linoleic acid • Linolenic acid • Can be used to make other fatty acids
    35. 35. Essential Fatty AcidsEssential Fatty Acids • Linoleic acid – Omega-6 fatty acid • Sources • Linolenic acid – Omega-3 fatty acid • Sources • DHA • EPA
    36. 36. Essential Fatty Acids • Eicosanoids • ‘Hormonelike” • Health benefits • Omega-6 to Omega-3 ratio • Fatty acid deficiencies • Symptoms
    37. 37. A Preview of Lipid MetabolismA Preview of Lipid Metabolism • Adipose cells store fat after meals • Lipoprotein lipase • Hydrolyzes triglycerides • Triglycerides reassembled inside adipose cells • Using fat for energy • Protein sparing • Energy deprivation • Fasting and ketone bodies
    38. 38. Health Effects of Saturated Fats,Health Effects of Saturated Fats, TransTrans Fats, and CholesterolFats, and Cholesterol • Current American diet • Blood lipid profile • Heart disease • Elevated blood cholesterol • Saturated fat – increase LDL cholesterol, promote blood clotting • Dietary choices • Trans fats – increase LDL cholesterol • Dietary cholesterol
    39. 39. Health Effects of Saturated Fats,Health Effects of Saturated Fats, TransTrans Fats, and CholesterolFats, and Cholesterol • Cancer • Promotion rather than initiation of cancer • Dietary fat and cancer risk • Differs for various types of cancer • Obesity • Cutting fat from diet reduces kcalories • Dietary recommendations
    40. 40. Recommended Intakes of SaturatedRecommended Intakes of Saturated Fat,Fat, TransTrans Fat, & CholesterolFat, & Cholesterol • DRI and Dietary Guidelines • Diet low in saturated and trans fat • Diet low in cholesterol • 20 to 35 percent of daily energy from fat • Daily Values (DV) on food labels • Saturated fat and cholesterol
    41. 41. Health Effects of MonounsaturatedHealth Effects of Monounsaturated & Polyunsaturated Fats& Polyunsaturated Fats • Heart disease • Replace saturated fats with unsaturated fats • Regular consumption of omega-3 fatty acids • Suppress inflammation • Cancer • Omega-3 fatty acids from food • Supplements
    42. 42. Replacing Saturated with Unsaturated Fat
    43. 43. Recommended Intakes ofRecommended Intakes of Mono- & Polyunsaturated FatsMono- & Polyunsaturated Fats • 20 to 35 percent of kcalories from fat • Includes essential fatty acids • AI have been established • DRI • Linoleic acid – 5-10% of daily energy • Linolenic acid – 0.6-1.2% of daily energy
    44. 44. From Guidelines to GroceriesFrom Guidelines to Groceries • Fat-soluble vitamins • A, D, E, and K • Flavor, texture, and palatability • Protein foods • Selections • Milk and milk products • Selections
    45. 45. Cutting Fat Cuts kCalories and Saturated Fat
    46. 46. From Guidelines to GroceriesFrom Guidelines to Groceries • Vegetables, fruits, and grains • Lowers consumption of various fats in the diet • Solid fats and oils • Fried and baked goods • Choose wisely • Unprocessed foods
    47. 47. From Guidelines to GroceriesFrom Guidelines to Groceries • Read food labels • Total fat, saturated fat, trans fat, and cholesterol • Compare products • % Daily Value vs. % kcalories from fat • Fat replacers • Types • Risks
    48. 48. High-Fat Foods –High-Fat Foods – Friend or Foe?Friend or Foe? Highlight 5Highlight 5
    49. 49. Guidelines for Fat IntakeGuidelines for Fat Intake • Limit saturated fat and trans fat intake • Moderate kcalories • Enough fat for good health • Not too much of the harmful fats • DRI recommendations • Compatible with low rates of disease
    50. 50. High-Fat Foods and HeartHigh-Fat Foods and Heart HealthHealth • Olive oil • Benefits for heart health • Replace saturated fats • Nuts • LDL cholesterol • Fat composition • Benefits for heart health • Cautious advice for dietary inclusion
    51. 51. High-Fat Foods and HeartHigh-Fat Foods and Heart HealthHealth • Fish • Omega-3 fatty acids • Benefits for heart health • Environmental contaminants • Dietary recommendations
    52. 52. High-Fat Foods and HeartHigh-Fat Foods and Heart DiseaseDisease • Saturated fat and LDL cholesterol • Sources of saturated fat in the U.S. • Meats • Whole milk products • Tropical oils • Zero saturated fat is not possible • Trans fat • Limit hydrogenated foods
    53. 53. High-Fat Foods and HeartHigh-Fat Foods and Heart DiseaseDisease
    54. 54. High-Fat Foods and HeartHigh-Fat Foods and Heart DiseaseDisease

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