1 / 93

Chapter 6: Lipids

Chapter 6: Lipids. Properties of Lipids. Do not readily dissolve in water Fats are solid at room temperature Oils are liquid at room temperature. Functions of Lipids. Provide energy Satiety Flavor and mouth feel Insulation Protect internal organs Transport fat-soluble vitamins

honorato-mcgowan
Download Presentation

Chapter 6: Lipids

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 6: Lipids

  2. Properties of Lipids Do not readily dissolve in water Fats are solid at room temperature Oils are liquid at room temperature

  3. Functions of Lipids • Provide energy • Satiety • Flavor and mouth feel • Insulation • Protect internal organs • Transport fat-soluble vitamins • Efficient storage of energy • 80% lipid, 20% protein and water

  4. Triglycerides Triglycerides are the main form of lipids in food and body (storage) Energy dense (9 kcal /g)

  5. Triglycerides Glycerol + 3 FA’s Triglyceride + 3 H20 H H--C--OH H--C--OH H--C--OH H O HO-C-R O HO-C-R O HO-C-R H O H--C--O--C-- O H--C--O--C-- O H--C--O--C-- H R + H2O + R + H20 R + H20

  6. Text art 06_02

  7. Structure Esterification Joining 3 fatty acids to a glycerol unit De-esterification Release of fatty acids-results in free fatty acids Diglyceride Loss of one fatty acid Monoglyceride Loss of two fatty acids

  8. Structure of Fatty Acids • Fatty acids • Function is dependent on: • Length • Degree of saturation • Location of double bonds • Configuration/Shape • Glycerol backbone

  9. Fatty Acid Chain Length • Long chain FA: > 12 Carbons • Predominant in food (meats, fish) • Medium chain FA: 6 - 10 Carbons • Account for ~4-10% of all FA • Short chain FA: < 6 Carbons • Found in dairy products

  10. Saturated Fatty Acid

  11. Monounsaturated Fatty Acid

  12. Polyunsaturated Fatty Acid

  13. Location of Double Bonds • Omega System • Double bond closest to omega (methyl) end • Omega: refers to the last carbon (methyl group) • Omega 6 vs Omega 3 fatty acids • Delta (alpha) System • Uses the carboxyl end and indicates location for all double bonds

  14. Fatty Acid Structure omega end alpha end H H H H H H H H H H H H H H H H H O H-C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C--C-C-OH H H H H H H H H H H H H H H H H H

  15. Fatty Acid Nomenclature

  16. Configuration/Shape cis versus trans

  17. Common Fatty Acids

  18. Saturated Fatty Acids • Fatty acids with no double bonds • Solid at room temperature • Animal fats: • Dairy: cheeses, ice cream, whole milk • Meat: beef, pork, lamb, • Plant/tropical oils (cottonseed, coconut) • Stearic, lauric, myristic, palmitic

  19. Saturated Fatty Acid

  20. Trans Fatty Acids risk for heart disease • Essentially a saturated fat • Raise LDL • Lower HDL • Intake has increased dramatically • Found in margarine, cookies, potato chips, snack chips, onion rings • Current intake is~3% of total kcals

  21. Hydrogenation of Fatty Acids Process used to solidify an oil Addition of hydrogen to an unsaturated fatty acid (eliminating the double bond—making it into a saturated fatty acid) Trans fatty acids are a by product of hydrogenation How can we limit intake of these?

  22. Figure 06_07

  23. Trans Fatty Acid

  24. Food Labels • % Daily Value on Nutrition Facts label is sum of trans and saturated fatty acids • Quantity of trans fatty acids • “Trans fat free” has no more than 0.5 g each of trans or saturated fat • Read the food label and look for hydrogenated or partially hydrogenated oils, or trans fatty acids

  25. Trans Fatty Acids

  26. Monounsaturated Fatty Acids One double bond Oleic acid (Omega 9) Olive oil, canola oil, nuts Rate of CHD low in Mediterranean countries where diet is rich in olive oil Diet high in MUFA equivalent to low-fat diet in ↓ LDL-C, but does not ↓ HDL-C

  27. Monounsaturated Fatty Acid

  28. Polyunsaturated Fatty Acids • 2 or more double bonds • Provides essential fatty acids (EFAs) • Omega 3 • Omega 6 • Properties differ between these EFAs

  29. Polyunsaturated Fatty Acid

  30. Figure 06_11

  31. Essential Fatty Acids • Polyunsaturated fatty acids • Body can only make double bonds after the 9th carbon from the omega end • Needed for • immune function • vision • cell membranes • production of hormone-like compounds

  32. Essential Fatty Acid Needs Adequate Intake Approximately 2-4 Tablespoons daily Deficiency Unlikely Toxicity No upper level set 32

  33. Omega-3 Fatty Acids Linolenic acid (α-linolenic acid) Forms eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) Metabolized to form eicosanoids

  34. Omega-3 Fatty Acids • Consumption of large amounts of omega-3 fatty acids decreases the ability of blood to clot • May: • Prevent stroke and heart attacks caused by clots (thrombosis) • Reduce risk of stroke caused by blood clots • Help some chronic inflammatory conditions • Asthma, rheumatoid arthritis, psoriasis

  35. Omega-3 Fatty Acids • Recommend intake of ~2 servings of fish/wk • Shellfish • Cold water/fatty fish (salmon, mackerel, sardines, tuna) • Consumption of canola or olive oil vs. other plant oils • Flaxseed oil • 2 tbsp per day • Fish oil capsules • 900 mg per day • Avoid: if have a history of bleeding disorder, on blood thinners

  36. Omega-6 Fatty Acids • Linoleic acid • Forms arachidonic acid • Metabolized to eicosanoids • Found in vegetable oils • Corn, sunflower, safflower, soybean oils, nuts, seeds, wheat germ • Only need ~ 1 tablespoon a day

  37. Eicosanoids • A group of hormone-like compounds • By-pass the blood stream and work in the area of origin • Regulators of: • Blood pressure • Clotting • Immune responses • Inflammatory responses • Stomach secretions • Prostaglandins, thromboxanes, leukotrienes, prostacyclins, lipoxins

  38. Eicosanoids Have Different Effects • Omega-3 eicosanoids, DHA, EPA • ↓ blood clotting • ↓ inflammatory responses • Reduce heart attack • Excess may cause hemorrhagic stroke • Omega-6 eicosanoids; Arachidonic acid • ↑blood clotting • ↑ inflammatory responses • Eicosanoids have different effects on different tissues

  39. American Heart Association Recommendations Total fat: <30% of total calories Saturated fat: <10% of total calories Monounsaturated fat: 10% of total calories Polyunsaturated fat: 10% of total calories Cholesterol: <300 mg/day

  40. Phospholipids Hydrophobic and Hydrophillic Ends Functions Component of cell membranes Eicosanoid synthesis Emulsifier Allows fats/lipids to be dispersed in water Bile acids Sources Synthesized by the body as needed Built on a glycerol backbone At least one fatty acid replaced with phosphorus compound Food: egg yolks (lecithin), wheat germ and peanuts

  41. Emulsifier Hydrophilic end (attracts water) Hydrophobic end (attracts lipid)

  42. Sterols Multi-ringed structure, most known is cholesterol Functions Bile acids, cell membranes Precursor of steroid hormones, sex hormones, adrenal hormones, Vitamin D Sources Synthesized by the liver Food: animal origin

  43. Lipid Digestion • Mouth • Lingual lipase (inactive until reaches stomach) • Stomach • Gastric lipase (digests primarily SCFAs) • Muscular contractions mix fat with digestive enzymes • Fats generally remain in stomach 2-4 hours

  44. Lipid Digestion • Small intestine • Cholecystokinin (CCK) and Secretin • Released due to presence of fat in duodenum • CCK stimulates release of • Pancreatic lipase • Bile (to help emulsify fat) • Secretin stimulates release of • Bicarbonate • Raises pH for activation of lipases

  45. Bile • Composed of bile acids, bile pigments, phospholipids (lecithin) • Synthesized from cholesterol in the liver • Function is to emulsify fat • Allows fat to be suspended in watery digestive juices • Large fat globules broken down to smaller ones, surface area for lipase action increases • Micelles are formed

More Related