Chapter 6: Lipids

  1. properties of lipids
    • do not dissolve in water but mix with oils
    • energy dense (9 kcal/g)
    • hydrophobic
  2. lipids are made of
    triglyceride, phospholipids, and sterols
  3. what are triglycerides
    • main form of lipids in food and body storage
    • glycerol with 3 fatty acids attached
  4. esterification
    joining 3 fatty acids to a glycerol unit
  5. de-esterification
    release of fatty acids -> results in free FA
  6. re-esterification
    reattaching a fatty acid
  7. 3 ways FA vary
    • # of carbons in the chain
    • extent to which the chain is saturated with hydrogen
    • shape of chain (straight vs bent)
  8. long chain fatty acids
    • > 12 carbons
    • fats on meat as well as most plant oils
    • longest to digest
    • transported via lymph not portal system
  9. medium chain fatty acids
    • 6-10 carbons
    • coconut and palm oil
    • digested almost as fast as glucose
    • transported via portal system
  10. short chain fatty acids
    • < 6 carbons
    • dairy fat
    • transported via portal system
    • rapidly digested
  11. saturated vs monounsaturated vs polyunsaturated FA
    • saturated - no double bonds
    • monounsaturated - one double bond
    • polyunsaturated - 2+ double bonds
  12. most common saturated FA
    stearic acid, which is found in animal fat
  13. common monounsaturated fatty acids (MUFA)
    • oleic acids
    • olive oil
    • canola oil
  14. common polyunsaturated fatty acids
    • linoleic acid
    • safflower
    • corn
    • soybean oil
  15. cis FA vs trans FA
    • cis - hydrogens are found on same side of double bond
    • trans - hydrogens on opposite sides of double bond
  16. hydrogenation
    • process of creating trans fat
    • H+ are added
    • this breaks the double bonds of unsaturated fats, allowing carbons to accept the hydrogens
    • this makes the fat more like saturated fat
  17. benefit of hydrogenation
    lipid becomes more stable
  18. health impacts of trans fat
    • increases the risk of heart disease and cancer
    • raises LDL and lowers HDL
    • increases inflammation
  19. omega naming system
    • uses methyl end to count to closest double bond
    • first # = number of carbons
    • second # = number of double bonds
    • third # = location of first double bond from methyl
  20. delta naming system
    • uses carboxyl end
    • indicates location for all double bonds
  21. what are the essential fatty acids and why are they called this
    • omega-3 FA
    • omega-6 FA
    • called this because they must be ingested, cannot be made by body
  22. what is an omega-3 FA and examples
    • 1st double bond is between 3rd and 4th carbons from methyl end
    • ex. alpha-linoleic acid -> found in fish, canola oil, walnuts, flax seeds
  23. what is omega-6 FA and examples
    • 1st double bond is between 6th and 7th carbons from methyl end
    • ex. linoleic acid -> safflower, corn, soybean oil
  24. what are omega-3 and 6 processed into in the body
    • omega-3 -> EPA and DHA
    • omega-6 -> dihomo-gamma-linoleic acid, arachidonic acid
    • both are then converted into eicosanoids
  25. what are eicosanoids
    • hormone like compounds in the body
    • such as prostaglandins, prostacyclins, thrombaxanes
  26. what do omega-3 and omega-6 eicosanoids do
    • omega 3 -> decrease blood clotting, reduce heart attack, excess can cause hemorrhagic stroke
    • omega 6 -> increase blood clotting, increase inflammatory response
  27. 4 functions of triglycerides
    • provide energy (9 kcal/g)
    • provide compact energy source
    • insulate and protect the body
    • aid fat soluble vitamin absorption and transport
  28. structure of phospholipid
    same structure as triglycerides but one FA is replaced with phosphorus-containing compound
  29. phospholipid functions (2)
    • primary component of cell membranes (phospholipid bilayer)
    • emulsifier of fats
  30. sources of phospholipids
    • made by liver or supplied by diet
    • food - egg yolks, wheat germs, peanuts
    • food sources are not essential as the liver produces enough phospholipids
  31. structure of sterols
    carbons mostly arranged in multi-ring structures
  32. most well known sterol
    • cholesterol
    • used to make sex hormones, active form of vitamin D, adrenal hormones (cortisol), and bile
  33. functions of sterol (2)
    • essential component of cell membranes (made by liver, found only in animal products)
    • forms important hormones - estrogen, testosterone, vitamin D
  34. sources of sterol
    • 1/3 comes from food, rest made by body
    • food - animal origin (meat, fish, poultry, eggs, dairy)
  35. RDI for total dietary fat
    20-35% of calories
  36. RDI of saturated fat
    as low as possible
  37. RDI of trans fat
    as low as possible
  38. RDI of unsaturated fat
    most of fat intake
  39. RDI of omega-6: linoleic acid
    5% of calories
  40. RDI of omega-3: alpha-linolenic acid
    0.6-1.2% of calories
  41. RDI for cholesterol
    as low as possible
  42. AHA recommends to limit saturated fat intake to
    7% of total calories
  43. AHA recommends to limit cholesterol intake to
    less than 200 mg daily
  44. what starts the digestion of fat in the mouth
    • lingual lipase
    • breaks down short and medium chained FA
  45. what digests fat in the stomach
    • gastric lipase
    • acts on triglycerides containing short and medium chained FA -> breaks them into mono+diglycerides + free FA
  46. what happens when fats get to the small intestine
    • CCK stimulates pancreas to release pancreatic lipase and colipase
    • CCK stimulates the release of bile to help emulsify fat to form micelles
    • pancreatic lipase - breaks down triglycerides into monoglycerides and free FA
    • collapse - helps lipase latch onto micelles to facilitate lipase enzyme action
  47. how are large fatty acids absorbed into the small intestine
    • bile emulsifies large FA into micelles
    • micelles are readily absorbed into the cells of the SI at the brush boarder
    • later re-esterified as triglycerides and enter the lymphatic system, where they are dumped into CV system at thoracic duct, near the heart
  48. how are small and medium sized FA absorbed in the small intestine
    • absorbed directly into the cells of the SI
    • absorbed via the portal vein and entire into the cardiovascular system directly
  49. why is increased bile excretion good
    helps lower blood cholesterol supply because when less is recycled, liver has to take more cholesterol out of the blood to restore bile supply
  50. how are lipids transported in the blood
    • lipid components repackaged into chylomicrons
    • which enter lymphatic circulation to reach bloodstream at thoracic duct
  51. receptor pathway
    • LDL is broken down and utilized in the body
    • receptors on cells surface bind to LDL
    • LDL taken up by endocytosis and broken down into protein and free cholesterol
    • excess becomes oxidized by free radicals (which is bad b/c oxidized LDL increases risk of CVD + metabolic syndrome)
  52. function of lipoprotein lipase
    • lipoprotein lipase on blood vessels walls break down triglycerides in the chylomicrons into fatty acids and glycerols
    • fatty acids are absorbed by cells -> used for energy and stored in adipose cells
  53. fat from the liver is transported as
    • lipoproteins
    • lipid core of cholesterol made from components of carbs, proteins, and free FA taken up from blood
    • shell composed of protein, phospholipid, triglycerides, and cholesterol
  54. what is VLDL
    very low density lipoprotein
  55. what happens to lipoprotein as lipid is lost
    the lipoprotein becomes more dense
  56. what does LPL do
    • lipoprotein lipase takes triglycerides from VLDL and moves it into cells
    • as lipid is lost, the lipoprotein becomes more dense
    • VLDL -> IDL -> LDL
  57. what is the primary component in LDL
  58. scavenger pathway for cholesterol uptake
    • removes oxidized LDL
    • scavenger WBCs remove oxidized LDL from circulation
    • prevents oxidized LDL from returning to circulation
    • cholesterol builds up in these cells can be deposited on walls of blood vessels (plaque)
    • build up of plaque on walls leads to atherosclerosis (hardening of the arteries)
  59. functions of HDL in cholesterol uptake
    • picks up cholesterol from dying cells and other sources
    • transfers cholesterol to other lipoproteins for transport to the liver for excretion
    • HDL can also transfer directly back to the liver
    • blocks oxidation of LDL
  60. benefits of high HDL level
    • remove cholesterol from the bloodstream
    • HDL may block oxidation of LDL
    • reduces risk of heart disease
    • pre-menopausal women have higher HDL
    • HDL level is indication of CV health
  61. health concern for high polyunsaturated fat intake
    greater than 10% intake increases cholesterol deposit in arteries and may block immune system
  62. health concern for excessive omega 3 fat intake
    more than 8 oz of source per day can impair immune system and cause excessive bleeding
  63. health concern of imbalances in omega 3 and omega 6 lipids
    • can cause inflammation
    • low intakes of omega 3 can worsen inflammatory diseases
  64. health concern of intaking rancid lipids
    • they have components that may damage cells
    • polyunsaturated fats go rancid more easily bc double bonds are easily damaged by oxygen/heat/metal/light
  65. effect of diets high in trans lipids
    • raises LDL
    • lowers HDL
    • increases inflammation
Card Set
Chapter 6: Lipids
ch 6