Klappa

Public flashcard deck · 107 cards

12.) Lipases: pancreatic, lipoprotein, hormone sensitive – their localization and roles, activating factors. Digestion and absorption of lipids in the GI tract.

Study this deck free Add to my library

  1. Front
    Lipids and water solubility
    Back
    Lipids are hydrophobic and therefore cannot be digested and transported like water-soluble nutrients
  2. Front
    Overall sequence of dietary lipid handling
    Back
    Emulsification by bile salts, enzymatic digestion by pancreatic enzymes, absorption into enterocytes, re-esterification, packaging into chylomicrons, and transport through lymph then blood
  3. Front
    Three major lipases in lipid metabolism
    Back
    Pancreatic lipase, lipoprotein lipase, and hormone-sensitive lipase
  4. Front
    Role of pancreatic lipase
    Back
    Digests dietary triacylglycerol in the intestine
  5. Front
    Role of lipoprotein lipase
    Back
    Hydrolyzes triacylglycerol in chylomicrons and VLDL in capillaries
  6. Front
    Role of hormone-sensitive lipase
    Back
    Mobilizes stored triacylglycerol in adipocytes
  7. Front
    Major dietary lipids
    Back
    Triacylglycerols, cholesterol and cholesterol esters, phospholipids, and free fatty acids
  8. Front
    Main dietary lipid
    Back
    Triacylglycerol
  9. Front
    Approximate fraction of dietary lipid that is triacylglycerol
    Back
    Up to 90%
  10. Front
    Main site of lipid digestion
    Back
    Small intestine
  11. Front
    Key helpers in intestinal lipid digestion
    Back
    Bile salts, pancreatic lipase, colipase, and pancreatic bicarbonate
  12. Front
    Hormone that stimulates release of bile and pancreatic enzymes
    Back
    Cholecystokinin (CCK)
  13. Front
    Hormone that stimulates bicarbonate secretion
    Back
    Secretin
  14. Front
    Where lipid digestion products go before absorption
    Back
    Through the unstirred water layer to the enterocyte surface
  15. Front
    Why bile salts are needed in lipid digestion
    Back
    Lipids are insoluble in water and must be emulsified
  16. Front
    Meaning of emulsification in lipid digestion
    Back
    Dispersing immiscible liquids into an emulsion
  17. Front
    Role of bile salts in lipid digestion
    Back
    Break large fat droplets into smaller droplets to increase surface area for lipase action
  18. Front
    Additional role of bile salts in lipid absorption
    Back
    Help form mixed micelles that deliver lipid digestion products to the enterocyte surface
  19. Front
    High-yield fact about bile salts
    Back
    Bile salts do not hydrolyze fat; they emulsify it and help absorption
  20. Front
    Site of secretion of pancreatic lipase
    Back
    Pancreas
  21. Front
    Site of action of pancreatic lipase
    Back
    Intestinal lumen of the small intestine
  22. Front
    Role of pancreatic lipase in intestinal digestion
    Back
    Digests dietary triacylglycerol
  23. Front
    Stepwise products of pancreatic lipase action on TAG
    Back
    Diacylglycerol, then 2-monoacylglycerol and free fatty acids
  24. Front
    High-yield final products of pancreatic lipase digestion
    Back
    2-monoacylglycerol and free fatty acids
  25. Front
    Key helper for pancreatic lipase
    Back
    Colipase
  26. Front
    Why colipase is needed for pancreatic lipase
    Back
    Bile salts coat lipid droplets and can interfere with lipase binding, so colipase helps lipase bind at the lipid-water interface
  27. Front
    Role of bicarbonate in pancreatic lipase function
    Back
    Neutralizes acidic chyme and provides a better pH for pancreatic enzymes
  28. Front
    Hormonal support for pancreatic lipase action
    Back
    CCK promotes delivery of pancreatic enzymes and bile, and secretin promotes bicarbonate secretion
  29. Front
    High-yield distinction for pancreatic lipase activation
    Back
    Pancreatic lipase works with colipase, not apo CII, and is not activated by phosphorylation
  30. Front
    Major absorbable products of intestinal lipid digestion
    Back
    Free fatty acids, 2-monoacylglycerols, cholesterol-related lipids, and other lipid products in micelles
  31. Front
    Vehicle that carries lipid digestion products to the microvilli
    Back
    Mixed micelles
  32. Front
    Path lipid digestion products take to enterocytes
    Back
    They move through the unstirred water layer to the luminal surface of enterocytes
  33. Front
    How long-chain fatty acids and monoacylglycerols enter enterocytes
    Back
    Mainly by passive diffusion
  34. Front
    Transporters that help long-chain fatty acid uptake
    Back
    FATP transporters
  35. Front
    When FATP is especially helpful
    Back
    At low luminal long-chain fatty acid concentration
  36. Front
    Intracellular binding protein for long-chain fatty acids in enterocytes
    Back
    FABP
  37. Front
    Destination of long-chain fatty acids inside enterocytes
    Back
    Smooth endoplasmic reticulum
  38. Front
    Absorption of short-chain and medium-chain fatty acids
    Back
    Absorbed directly into intestinal cells without bile salts
  39. Front
    Transport route of short-chain and medium-chain fatty acids
    Back
    Portal vein to the liver
  40. Front
    Handling of long-chain fatty acids after absorption
    Back
    They are re-esterified in enterocytes and leave in chylomicrons
  41. Front
    High-yield absorption distinction
    Back
    SCFA and MCFA go to portal blood, whereas LCFA go to chylomicrons and lymph
  42. Front
    What happens to FFA and MAG in enterocytes
    Back
    They are recombined back to triacylglycerol in the smooth ER
  43. Front
    What happens to triacylglycerol after re-esterification in enterocytes
    Back
    It is packaged with other lipids and apoproteins into chylomicrons
  44. Front
    Route of chylomicron خروج from enterocytes
    Back
    Into the lymphatic system and then into the blood
  45. Front
    High-yield summary of long-chain dietary fat handling
    Back
    Digested, absorbed, re-esterified, and exported as chylomicrons
  46. Front
    Where chylomicrons first enter after leaving enterocytes
    Back
    Lymphatic capillaries in the intestinal villi
  47. Front
    Path of chylomicrons from lymph to blood
    Back
    Through lymph to the thoracic duct and then into the subclavian vein
  48. Front
    Main job of chylomicrons
    Back
    Transport dietary triacylglycerols to peripheral tissues
  49. Front
    Localization of lipoprotein lipase (LPL)
    Back
    Attached to the luminal surface of endothelial cells in capillaries by proteoglycans or heparan sulfate
  50. Front
    Major tissues associated with LPL
    Back
    Adipose tissue, skeletal muscle, heart muscle, lactating mammary gland, lung, kidney, and liver
  51. Front
    High-yield location fact for LPL
    Back
    LPL is not in the intestinal lumen or inside adipocyte cytosol; it acts on the capillary lumen side
  52. Front
    Role of LPL
    Back
    Hydrolyzes the triacylglycerol core of circulating lipoproteins
  53. Front
    Main lipoprotein substrates for LPL
    Back
    Chylomicrons and VLDL
  54. Front
    Products of LPL action
    Back
    Free fatty acids and glycerol
  55. Front
    Fate of fatty acids released by LPL in adipose tissue
    Back
    Stored as triacylglycerol
  56. Front
    Fate of fatty acids released by LPL in muscle and heart
    Back
    Oxidized for energy
  57. Front
    Approximate fraction of lipoprotein core TAG degraded by LPL
    Back
    About 90%
  58. Front
    Direct activator of LPL
    Back
    Apo CII
  59. Front
    Source of apo CII for chylomicrons and VLDL
    Back
    HDL
  60. Front
    Effect of insulin on LPL
    Back
    Stimulates LPL synthesis and secretion to the capillary lumen, especially in adipose tissue
  61. Front
    High-yield regulation summary for LPL
    Back
    LPL activator is apo CII, insulin increases it, and LPL acts on circulating TAG rather than stored adipocyte TAG
  62. Front
    Tissue difference in LPL according to lecture
    Back
    Muscle LPL has low Km and adipose LPL has high Km
  63. Front
    Functional implication of muscle versus adipose LPL
    Back
    Muscle uses fatty acids readily for oxidation, whereas adipose tissue stores them
  64. Front
    Localization of hormone-sensitive lipase (HSL)
    Back
    Inside adipocytes at lipid droplets
  65. Front
    High-yield location distinction between HSL and LPL
    Back
    HSL is inside adipose cells, whereas LPL is outside on capillary endothelium
  66. Front
    Role of HSL
    Back
    Mobilizes stored triacylglycerol during fasting or energy demand
  67. Front
    Products of adipose triacylglycerol hydrolysis by HSL
    Back
    Free fatty acids and glycerol
  68. Front
    Transport form of fatty acids released from adipose tissue
    Back
    Bound to albumin in the blood
  69. Front
    High-yield HSL summary
    Back
    HSL mobilizes stored fat and mediates lipolysis in adipose tissue
  70. Front
    Mechanism of HSL activation
    Back
    Hormonal signaling through cAMP and protein kinase A (PKA)
  71. Front
    Classic fasting hormones that activate HSL
    Back
    Glucagon and adrenaline or epinephrine
  72. Front
    Sequence of signaling that activates HSL
    Back
    Hormone activates adenylate cyclase, cAMP rises, PKA activates lipolysis, and the HSL or perilipin system promotes access to stored TAG
  73. Front
    Effect of insulin on HSL and lipolysis
    Back
    Insulin inhibits lipolysis and opposes HSL action
  74. Front
    High-yield regulation summary for HSL
    Back
    HSL is activated by glucagon or epinephrine through cAMP and PKA and inhibited by insulin
  75. Front
    Comparison of pancreatic lipase, LPL, and HSL
    Back
    Pancreatic lipase acts in the intestinal lumen on dietary TAG, LPL acts on capillary endothelium on TAG in chylomicrons and VLDL, and HSL acts inside adipocytes on stored TAG
  76. Front
    Location of pancreatic lipase
    Back
    Intestinal lumen
  77. Front
    Substrate of pancreatic lipase
    Back
    Dietary triacylglycerol
  78. Front
    Products of pancreatic lipase
    Back
    2-monoacylglycerol and free fatty acids
  79. Front
    Helper for pancreatic lipase
    Back
    Colipase
  80. Front
    Indirect helpers for pancreatic lipase
    Back
    Bile salts and a bicarbonate-supported intestinal environment
  81. Front
    Location of LPL
    Back
    Luminal surface of capillary endothelium
  82. Front
    Substrate of LPL
    Back
    Triacylglycerol in chylomicrons and VLDL
  83. Front
    Products of LPL
    Back
    Free fatty acids and glycerol
  84. Front
    Activator of LPL
    Back
    Apo CII
  85. Front
    Hormonal stimulation of LPL
    Back
    Insulin
  86. Front
    Location of HSL
    Back
    Adipocyte lipid droplets
  87. Front
    Substrate of HSL
    Back
    Stored triacylglycerol
  88. Front
    Products of HSL
    Back
    Free fatty acids and glycerol
  89. Front
    Activators of HSL
    Back
    Glucagon and epinephrine through cAMP and PKA
  90. Front
    Hormone that inhibits HSL
    Back
    Insulin
  91. Front
    Step-by-step sequence of lipid digestion and absorption
    Back
    Dietary lipids enter small intestine, CCK stimulates gallbladder and pancreas, secretin stimulates bicarbonate, bile salts emulsify lipid droplets, pancreatic lipase and colipase digest TAG to 2-MG and FA, products form mixed micelles and cross the unstirred water layer to enterocytes, LCFA and MAG enter enterocytes while SCFA and MCFA go directly to portal blood, LCFA and MAG are re-esterified to TAG in smooth ER, TAG is packaged into chylomicrons, chylomicrons enter lymph then blood, and LPL hydrolyzes chylomicron TAG in capillaries
  92. Front
    Fraction of bile salts reabsorbed according to lecture
    Back
    About 95%
  93. Front
    What happens to reabsorbed bile salts
    Back
    They circulate back to the liver
  94. Front
    High-yield fact about bile salt recycling
    Back
    Bile salts are reused rather than lost after one meal
  95. Front
    Very high-yield fact about pancreatic lipase
    Back
    Pancreatic lipase digests dietary TAG in the intestine
  96. Front
    Very high-yield fact about colipase
    Back
    Colipase helps pancreatic lipase
  97. Front
    Very high-yield fact about LPL location
    Back
    LPL is on capillary endothelium, not inside cells
  98. Front
    Very high-yield fact about LPL activation
    Back
    Apo CII activates LPL
  99. Front
    Very high-yield fact about insulin and LPL
    Back
    Insulin stimulates LPL in adipose tissue
  100. Front
    Very high-yield fact about HSL
    Back
    HSL mobilizes stored adipose TAG
  101. Front
    Very high-yield fact about HSL regulation
    Back
    Glucagon and epinephrine activate HSL, whereas insulin inhibits it
  102. Front
    Very high-yield absorption distinction for fatty acids
    Back
    LCFA leave the intestine in chylomicrons, whereas SCFA and MCFA go by portal vein
  103. Front
    Very high-yield transport fact about chylomicrons
    Back
    Chylomicrons enter lymph first and then blood
  104. Front
    Cheat-sheet pancreatic lipase
    Back
    Location is intestinal lumen, role is digestion of dietary TAG, products are 2-MG and free fatty acids, helper is colipase, and indirect helpers are bile salts and a bicarbonate-supported environment
  105. Front
    Cheat-sheet lipoprotein lipase
    Back
    Location is luminal surface of capillary endothelium, role is hydrolysis of TAG in chylomicrons and VLDL, products are fatty acids and glycerol, activator is apo CII, and insulin increases it
  106. Front
    Cheat-sheet hormone-sensitive lipase
    Back
    Location is adipocytes, role is mobilization of stored TAG, activators are glucagon and epinephrine through cAMP and PKA, and insulin inhibits it
  107. Front
    Cheat-sheet lipid digestion and absorption
    Back
    Bile salts emulsify, pancreatic lipase digests, micelles deliver products, LCFA are re-esterified in enterocytes, chylomicrons are formed, and transport proceeds from lymph to blood

Study these 107 cards with spaced repetition. Klappa is a free flashcard app: it schedules every card with FSRS-6, studies a deck as flashcards, multiple choice, typed answers or a graded test, and imports your Anki decks. How Klappa schedules reviews.

Sign in to study