Lecture 4 Lipid Metabolism

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  1. Are lipids hydrophobic or hydrophilic ?

  2. Where do lipids began to digest ?

    What enzyme digests lipids ?

  3. What molecule is this ?
    Fatty Acid
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    Fatty Acid
  4. What molecule is this ?
    Fatty Acid
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  5. What molecule is this ?
    Fatty Acid
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  6. What molecule is ?
    Fatty Acid
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  7. What molecule is this ?
    Fatty Acid
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  8. What emulsifies fat in the duodenum of
    the small intestine ?

    Why is fat emulsified ?
    Bile Salts 

    In order to make portions smaller for absorption

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  9. What degrades the dietary lipids ?

    What enzyme degrades TAGs ?
    Pancreatic enzymes

    Pancreatic Lipase
  10. Why do the dietary lipids get degraded
    by pancreatic enzymes ?

    Where does the pancreatic lipase
    preferentially cleave the Fatty Acids from Triacylglycerol ?
    They are too large for digestion and absorption by enterocytes

    C1 and C3
  11. What hydrolyzes ( Cholsteryl ester )
    into ( Cholesterol and Fatty acids ) ?
    Cholesteryl esterase 

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  12. In terms degradation of dietary lipids by
    pancreatic enzymes what enzyme removes a single Fatty Acid from C2 of a TAG leaving a lysophospholipid ?

    In terms degradation of dietary lipids by
    pancreatic enzymes what enzyme removes the FA at C1 leaving a glycerophosphoryl base ?
    Phospholipase A2

  13. What are the two hormonal control for
    lipid digestion in the small intestine ?
    Cholecystokinin and Secretin
  14. What is the function of Secretin ?
    Promotes Bicarbonate secreton into the small intestine
  15. What is the function of  Cholecystokinin ?
    • -Stops Gastric Motility
    • -Promotes Secretion of Bile and Pancreatic Enzymes
  16. What is the composition of mixed
    micelles ?

    What is the primary site for lipid
    absorption ?
    Lipids , bile salts , and fat soluble vitamins

    Brush border membrane
  17. Where does resynthesis of TAG
    and cholesterol esters take place ?
    Endoplasmic Reticulum
  18. What is it called when a person has lipid
    in their feces ?
  19. Newly resynthesized TAGs and cholesteryl esters are very hydrophobic, and
    aggregate in an aqueous environment
    so they are packaged in ?
  20. Since Chylomicorns are to big for blood vessels where do they go ?
    Lymphatic vessels
  21. Explain the route in which Triacylglycerols enter the enterocytes to the lymphatic vessels ?
    Pacnreatic Lipase> Fatty acids + Monoglycerol > 2 Fatty acyl-CoA +Monoacyl-glycerol > Triacylglycerol > Chylomicrons

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  22. What are the different forms that FA’s
    exist in the body ?

    Free Fatty Acids can be oxidized by
    many tissues to produce energy ,particularly by what organs ?
    • -Free fatty acids 
    • Fatty acyl esters in TAGs

    -Liver and Muscle
  23. What makes a fatty acid amphipathic ?
    A fatty acid consists of a hydrophobic hydrocarbon chain with a terminal hydrophilic carboxyl group. 

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  24. What is the percentage of Fatty acid
    esters found in plasma ?
  25. What are fatty acids ?

    How long do they tend to be ?
    Monocarboxylic acids that typically contain hydrocarbon chains of variable lengths 

    Between 12 and 20 or more carbons
  26. How are fatty acids numbered ?

    Where do you usually find fatty acids ?
    From the carboxylate end 

    triacylglycerols and several types of membrane bound lipid molecules
  27. What are saturated vs unsaturated fatty acid chains ?
    Fatty acid chains that contain only carbon-carbon single bonds are termed saturated

    Fatty acid chains that contain one or more double bonds are termed unsaturated
  28. What form tends to persist when discussing fatty acids , Cis or Trans ?
  29. Why are cis double bonds better ?
    cis double bonds cause an inflexible “kink” in a FA chain, therefore unsaturated Fats do not pack as tightly together and have a lower melting point (liquids at room temp.)
  30. How does hydrocarbon chain length
    change the melting point ?

    How many spaces do Double bonds have to
    be spaced ?
    Longer the chain the higher the melting point

    3 carbon intervals
  31. Make this acid ?

    Arachidonic acid, 20:4 (5,8,11,14)
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  32. What is the difference between linoleic acid and a-linolenic acid ?
    Linoleic acid - 18:2 (9, 12)

    a-linolenic acid - 18:3 (9, 12, 15)
  33. What are the two essential FA’s ? 

    What are FA’s that can be synthesized
    by the body called  ?
    -Linoleic acid and a-linolenic acid 

    -Nonessential FA’s
  34. Carbohydrates and proteins obtained
    from  the diet in excess of the body’s needs can be converted to fatty acids which are 
    stored as ?
  35. In adults where does fatty acid
    synthesis occur ?
    • Liver (mainly)
    • Lactating mammary glands 
    • Adipose tissue (to a lesser extent)
  36. Where does fatty acid occur within a
    cell ?

    How are carbons incorporated into a
    chain ? Does this require energy ?

    They are added using acetyl CoA , yes ATP and NADPH
  37. How many units are added at one time to
    the growing carbon chain ?
    Two-carbon units
  38. In order for Acetyl CoA to make it out of the mitochondria for fatty acid synthesis what does it have to be changed into ?

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  39. Fatty acid synthesis  is in cytosol , 
    Breakdown /beta oxidation is in the ?

    Where does the actyl-CoA come
    from to build the fatty acid in the cytosol ?
    Mitochondrial Matrix

  40. Explain Fatty acid Synthesis ?
    1- synthesis of acetyl ACP  and malonyl ACP from acetyl CoA

    • 2-Acetoacetyl-ACP formation of a 4 carbon unit attached
    • to ACP, 


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  41. FAS
    is a multifunctional enzyme, the enzyme activities listed are separate catalytic
    domains present in each FAS monomer
    no answer , case and point
  42. After palmitic acid how many more carbons can be added ?

    Where does this take place ?
    2 carbons

    Endoplasmic Reticulum
  43. What is the function of desaturases ?

    Where does desaturase usually place the first double bond ? Can it go past Carbon 9 ?
    They add cis double bonds 

    Usually inserted between carbons 9 and 10 , no it can not.
  44. In terms of a Triacylglycerol what
    does mono , di , and tri stand for ?

    What is a species of acylglycerol called when it is a solid at room temperature , how about a liquid and room temprature ?
    one, two or three molecules of fatty acid esterified to a molecule of glycerol

    • Fat
    • Oil
  45. The 3 fatty acids esterified to a glycerol
    molecule are usually not of the same type What are they usually ?
    • Carbon #1 is typically saturated
    • Carbon #2 is typically unsaturated
    • Carbon #3 can be either
  46. TAGs are only slightly soluble in water
    and cannot form stable micelles by themselves so they coalesce with ?
    They coalesce within adipocytes to form oily droplets that are nearly anhydrous
  47. What is the initial acceptor of FAs during TAG synthesis ?
    glycerol phospahte
  48. What does a FA have to be attached to
    in order for in to participate in TAG synthesis ?

    What family of enzymes catalyze this
    reaction ?

    fatty acyl CoA synthetases
  49. How is TAG stored in adipose ?

    How much TAG is stored in the Liver ?
    It is stored in anhydrous form

    Very little
  50. Where is TAG stored as the major source
    of energy for the body ?

    The oxidation of fatty acids provide
    how much Kcal/gram ?
    Adipose Tissue

    9 Kcal/gram
  51. The mobilization of stored fat requires the hydrolytic release of fatty acids and glycerol from their TAG form. This process is
    initiated by what enzyme ?
    hormone-sensitive lipase.
  52. Where does the enzyme hormone-sensitive
    lipase cleave the fatty acid from on a Triacylglycerol ?
    removes a fatty acid from carbon 1 and or carbon 3 of the TAG
  53. The major pathway for catabolism of
    fatty acids is a pathway called ?
  54. Transport of long chain fatty acids (LCFA) into the mitochondria via what shuttle ? 

    How do short chains get across ?
    Carnitine shuttle

  55. In B-oxidation the Two-carbon fragments that are successively removed from
    the carboxyl end of a fatty acid is ?
    fatty acyl CoA, producing acetyl CoA
  56. Where do Very long chain fatty
    acids (22 carbons or longer) undergo a preliminary β-oxidation ?
  57. Liver mitochondria have the capacity to convert acetyl CoA derived from fatty acid oxidation into ?
    ketone bodies
  58. A person who has diabetes has a problem with carbohydrate catabolism what will you see ?
    Ketone bodies being produced because of lipid breakdown.
  59. What energy sources does the brain use ?
    ketones and glucose
  60. What does HMG CoA synthase do ?
    Makes Acetyl-CoA and Acetoacetate
  61. What makes the Fruity odor from beta oxidation?  

    During a fast, the liver is flooded with fatty acids mobilized from where  ?

    When the rate of formation of ketone bodies is greater than the rate of their use, their levels begin to rise in the blood , what is it called ? eventually,it increases in the urine
    what is it called ?


    ketonemia - ketouria
  62. What are the predominant lipids of cell
    membranes ?
  63. Name these Phosplipid compunds ?

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  64. What is cardiolipin’s composition ?
    Two molecules of phosphatidic acid (PA) esterified through their phosphate groups to an additional molecule of glycerol is called cardiolipin 

    • Cardiolipin is antigenic and is
    • recognized by antibodies raised against Treponema pallidum (bacterium that
    • causes syphilis)

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  65. Where does phospholiase A2 cleave ?
    Where does phospholiase A1 cleave ?
    Where does phospholiase D cleave ?
    Where does phospholiase C cleave ?
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  66. What does sphingomyelinase cut ?
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  67. How do you tell the difference between glycosphingolipid and Sphingomyelin ?
    Sphingomyelin has the choline group 

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  68. How do you tell a glycolipid ?
    • Look for glycosidic bond
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  69. What is the charge of this group ?

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  70. Degradation of sphingolipids , know these two enzymes.
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  71. Prostaglandins and thromboxanes are derived from what ?
    arachidonic acid or eicosapentaenoic acid (EPA)
  72. The first step in the synthesis of prostaglandins is the oxidative cyclization of free arachidonic
    acid to yield PGH2 by what enzymes ?
    • COX-1 (constitutive) and
    • COX-2 (nonconstitutive)

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  73. Leukotrienes can be synthesized
    from AA by what enzyme ?
  74. What is cholesterol ?
    It is a steroid alcohol
  75. What is the function of cholesterol ?
    • 1)structural component of membranes,
    • modulating fluidity

    • 2)precursor of bile acids, steroid
    • hormones and vitamin D
  76. What is the difference between Cholesteryl esters  and Sterols  ?
    1.Cholesteryl esters  are an esterified form (with a fatty acid attached at carbon 3).

    • 2. Sterols are steroids with a
    • 8 to 10 carbon, branched hydrocarbon chain attached to carbon 17 of the D ring
    • and OH group at carbon 3 on ring A

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  77. What is the main enzyme for cholesterol synthesis ?

    What can act as an inhibitor for this process
    HMG-CoA reductase is the key enzyme for cholesterol synthesis.

    Cholesterol itself
  78. What is the general process for cholesterol synthesis ?
    Mevalonate > Squalene > Cholesterol
  79. How does the body remove cholesterol ?
    It has to be turned into bile salts first. It can not be metabolized into CO2 and H2O.
  80. What is HDL ?
    • –Transports cholesterol from peripheral tissues  to the liver
    • -“Good cholesterol "
  81. What is LDL ?
    • –Transport cholesterol to tissues
    • –“Bad cholesterol”
  82. What is VLDL ?
    • –Produced in the liver
    • –Transport lipids from liver to peripheral tissues
    • –When depleted become LDLs.
  83. What are Chylomicrons ?
    • –Assembled in the intestine
    • –Transport  lipids from intestine to peripheral tissues
  84. What are exogenous lipids ?
    The lipids from the diet
  85. What molecule is this ?
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  86. What molecule is this ?
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  87. What molecule is this ?
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  88. What molecule is this ?
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  89. What molecule is this ?
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Card Set
Lecture 4 Lipid Metabolism
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