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11.) Lipids: structures of major lipids: triacylglycerols (TAG), phosphatidylserine, phosphatidylcholine, sphingomyelin, cholesterol and its main derivatives. Lipid soluble vitamins.

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  1. Front
    Major lipid classes in this topic
    Back
    Storage lipids are mainly triacylglycerols, membrane lipids are mainly phospholipids and sphingolipids, sterols are mainly cholesterol, and fat-soluble vitamins are A, D, E, and K
  2. Front
    Structural mindset for triacylglycerol
    Back
    Triacylglycerol is glycerol plus 3 fatty acids
  3. Front
    Structural mindset for glycerophospholipid
    Back
    Glycerophospholipid is glycerol plus 2 fatty acids plus phosphate plus a head group
  4. Front
    Structural mindset for sphingomyelin
    Back
    Sphingomyelin has a sphingosine backbone rather than glycerol
  5. Front
    Structural mindset for cholesterol
    Back
    Cholesterol is a rigid 4-ring sterol
  6. Front
    Storage lipid in the major classification
    Back
    Triacylglycerol
  7. Front
    Major membrane lipids in this topic
    Back
    Phosphatidylcholine, phosphatidylserine, sphingomyelin, and cholesterol
  8. Front
    Triacylglycerol structure
    Back
    Glycerol backbone esterified to 3 fatty acids
  9. Front
    Number of ester bonds in triacylglycerol
    Back
    Three ester bonds
  10. Front
    Key structural feature absent from triacylglycerol
    Back
    No phosphate head group
  11. Front
    Polarity of triacylglycerol
    Back
    Highly hydrophobic and nonpolar
  12. Front
    Why triacylglycerol is used for storage
    Back
    Its nonpolar hydrophobic structure makes it suitable for storage rather than membrane bilayers
  13. Front
    Main storage form and largest energy reserve in the body
    Back
    Triacylglycerol
  14. Front
    High-yield triacylglycerol summary
    Back
    Triacylglycerol is glycerol plus 3 fatty acids, is a storage lipid, has no phosphate, and is not amphipathic
  15. Front
    Main storage site of triacylglycerol
    Back
    Adipose tissue
  16. Front
    Major lipoproteins carrying triacylglycerol
    Back
    Chylomicrons and VLDL
  17. Front
    Major lipid component of the human diet
    Back
    Dietary triacylglycerol
  18. Front
    Approximate fraction of dietary lipid that is triacylglycerol
    Back
    Up to 90%
  19. Front
    Common structural pattern of glycerophospholipids
    Back
    Glycerol backbone with 2 fatty acids, phosphate on carbon 3, and a head group attached to the phosphate
  20. Front
    Amphipathic nature of glycerophospholipids
    Back
    They have hydrophobic fatty acid tails and a polar head group
  21. Front
    Why glycerophospholipids are ideal membrane lipids
    Back
    Their amphipathic structure allows membrane bilayer formation
  22. Front
    Phosphatidylcholine classification
    Back
    Phosphatidylcholine is a glycerophospholipid
  23. Front
    Structure of phosphatidylcholine
    Back
    Glycerol backbone, 2 fatty acids, phosphate, and choline head group
  24. Front
    Other name for phosphatidylcholine
    Back
    Lecithin
  25. Front
    Major structural phospholipid of mammalian membranes
    Back
    Phosphatidylcholine
  26. Front
    Approximate proportion of membrane phospholipid that is phosphatidylcholine
    Back
    Often 40% to 50%
  27. Front
    High-yield summary of phosphatidylcholine
    Back
    Phosphatidylcholine is lecithin, is a major membrane phospholipid, and has choline as its head group
  28. Front
    Important role of phosphatidylcholine
    Back
    Major structural membrane phospholipid
  29. Front
    Most important organic components of bile
    Back
    Phosphatidylcholine and bile salts
  30. Front
    Major component of lung surfactant
    Back
    Dipalmitoylphosphatidylcholine
  31. Front
    Function of dipalmitoylphosphatidylcholine in lung surfactant
    Back
    Prevents collapse of alveoli
  32. Front
    Phosphatidylserine classification
    Back
    Phosphatidylserine is a glycerophospholipid
  33. Front
    Structure of phosphatidylserine
    Back
    Glycerol backbone, 2 fatty acids, phosphate, and serine head group
  34. Front
    Membrane leaflet enriched in phosphatidylserine
    Back
    Inner leaflet of the plasma membrane
  35. Front
    Charge of phosphatidylserine
    Back
    Net negative charge
  36. Front
    Importance of phosphatidylserine charge
    Back
    Contributes to membrane potential and binding of positively charged molecules
  37. Front
    High-yield summary of phosphatidylserine
    Back
    Phosphatidylserine is a glycerophospholipid with a serine head group, a net negative charge, and enrichment in the inner leaflet
  38. Front
    Comparison of phosphatidylcholine and phosphatidylserine
    Back
    Both are glycerophospholipids, but phosphatidylcholine has choline as head group whereas phosphatidylserine has serine and carries a net negative charge
  39. Front
    Sphingomyelin classification
    Back
    Sphingomyelin is a sphingophospholipid, not a glycerophospholipid
  40. Front
    Backbone of sphingomyelin
    Back
    Sphingosine
  41. Front
    Key structural difference between sphingomyelin and glycerophospholipids
    Back
    Sphingomyelin uses sphingosine rather than glycerol as the backbone
  42. Front
    Formation of ceramide
    Back
    Sphingosine plus fatty acid joined by an amide bond forms ceramide
  43. Front
    Formation of sphingomyelin
    Back
    Ceramide plus phosphocholine forms sphingomyelin
  44. Front
    Structural logic of sphingomyelin
    Back
    Sphingosine plus fatty acid gives ceramide, and ceramide plus phosphocholine gives sphingomyelin
  45. Front
    High-yield sphingomyelin concept
    Back
    Sphingomyelin contains phosphocholine like phosphatidylcholine, but its backbone is sphingosine rather than glycerol
  46. Front
    Role of sphingomyelin
    Back
    Major membrane lipid
  47. Front
    Tissue association of sphingomyelin
    Back
    Prominent in myelin and nervous tissue membranes
  48. Front
    Ceramide structure
    Back
    Ceramide is sphingosine plus a fatty acid in amide linkage
  49. Front
    Importance of ceramide
    Back
    It is the core precursor for sphingomyelin and glycosphingolipids
  50. Front
    Cholesterol classification
    Back
    Cholesterol is a sterol
  51. Front
    Lecture structural description of cholesterol
    Back
    Alicyclic compound based on perhydrocyclopentanophenanthrene
  52. Front
    Simplified structural description of cholesterol
    Back
    4-ring steroid nucleus with 3 six-membered rings and 1 five-membered ring
  53. Front
    Key structural features of cholesterol
    Back
    One hydroxyl group, rigid hydrophobic ring system, and short hydrocarbon tail
  54. Front
    Positioning of cholesterol in membranes
    Back
    The hydroxyl group lies in the hydrophilic region and the steroid nucleus lies in the hydrophobic core
  55. Front
    High-yield cholesterol structure
    Back
    Cholesterol is a rigid 4-ring sterol with one OH group
  56. Front
    Major membrane role of cholesterol
    Back
    Stabilizing component of biological membranes
  57. Front
    Approximate fraction of plasma membrane lipids that may be cholesterol
    Back
    Up to about 30%
  58. Front
    Effect of cholesterol on membrane properties
    Back
    Maintains membrane fluidity and stability
  59. Front
    Major biosynthetic products derived from cholesterol
    Back
    Bile acids, steroid hormones, and vitamin D
  60. Front
    Formation of bile acids from cholesterol
    Back
    Cholesterol is converted in the liver to bile acids
  61. Front
    Examples of bile acids from the lecture
    Back
    Chenodeoxycholic acid, lithocholic acid, and deoxycholic acid
  62. Front
    How bile salts are formed
    Back
    Bile acids are conjugated with glycine or taurine
  63. Front
    Cholesterol as precursor of steroid hormones
    Back
    All steroid hormones are derived from cholesterol
  64. Front
    Carbon numbers of major steroid hormone classes
    Back
    Glucocorticoids and mineralocorticoids are 21C, androgens are 19C, and estrogens are 18C
  65. Front
    Cholesterol as precursor of vitamin D
    Back
    Cholesterol is a precursor for vitamin D hormone
  66. Front
    High-yield cholesterol derivative summary
    Back
    Main cholesterol derivatives are bile acids, steroid hormones, and vitamin D
  67. Front
    Fat-soluble vitamins
    Back
    Vitamins A, D, E, and K
  68. Front
    How fat-soluble vitamins are absorbed
    Back
    Absorbed with dietary lipids
  69. Front
    How fat-soluble vitamins are transported after absorption
    Back
    Carried in chylomicrons
  70. Front
    Vitamin A classification
    Back
    Vitamin A is a fat-soluble vitamin
  71. Front
    Important forms of vitamin A
    Back
    Retinol, retinal, retinoic acid, retinyl esters, and β-carotene
  72. Front
    Retinol
    Back
    Alcohol form of vitamin A
  73. Front
    Retinal
    Back
    Aldehyde form of vitamin A
  74. Front
    Retinoic acid
    Back
    Acid form of vitamin A
  75. Front
    Retinyl esters
    Back
    Storage form of vitamin A
  76. Front
    β-Carotene
    Back
    Provitamin A from plants
  77. Front
    Structural feature of retinol
    Back
    Contains a β-ionone ring with an unsaturated side chain
  78. Front
    Key functions of vitamin A
    Back
    Vision, growth and reproduction, maintenance of epithelial tissues, and immune function
  79. Front
    High-yield vitamin A associations
    Back
    Retinal is the vision form, retinoic acid regulates gene expression, and retinyl ester is the storage form
  80. Front
    Vitamin D classification
    Back
    Vitamin D is a fat-soluble vitamin and behaves like a hormone
  81. Front
    Active hormone form emphasized in the lecture
    Back
    1,25(OH)2D hormone
  82. Front
    Role of UVB in vitamin D metabolism
    Back
    UVB contributes to vitamin D formation
  83. Front
    Enzyme forming the active vitamin D hormone
    Back
    1α-hydroxylase (CYP27B1)
  84. Front
    Transport protein for vitamin D
    Back
    Vitamin D-binding protein (DBP)
  85. Front
    Major role of vitamin D
    Back
    Regulation of calcium and phosphate homeostasis and bone mineral metabolism
  86. Front
    High-yield vitamin D summary
    Back
    Vitamin D behaves like a hormone and mainly regulates calcium, phosphate, and bone metabolism
  87. Front
    Vitamin E classification
    Back
    Vitamin E is a fat-soluble vitamin
  88. Front
    Natural forms of vitamin E
    Back
    Eight naturally occurring tocopherols
  89. Front
    Most active form of vitamin E
    Back
    α-Tocopherol
  90. Front
    Major function of vitamin E
    Back
    Antioxidant
  91. Front
    What vitamin E helps prevent
    Back
    Oxidation of LDL and peroxidation of polyunsaturated fatty acids by oxygen and free radicals
  92. Front
    High-yield vitamin E summary
    Back
    Vitamin E is an antioxidant that protects membrane lipids from oxidative damage
  93. Front
    Vitamin K classification
    Back
    Vitamin K is a fat-soluble vitamin
  94. Front
    Active forms of vitamin K
    Back
    Phylloquinone (K1) from plants and menaquinone (K2) from intestinal bacteria
  95. Front
    Major biochemical function of vitamin K
    Back
    Required for posttranslational carboxylation of glutamate residues in several proteins
  96. Front
    Most testable role of vitamin K
    Back
    Synthesis of functional blood clotting proteins including prothrombin (factor II), VII, IX, and X
  97. Front
    Function of γ-carboxyglutamate residues formed with vitamin K
    Back
    Bind Ca2+ and allow clotting proteins to bind membranes
  98. Front
    High-yield vitamin K summary
    Back
    Vitamin K is required for clotting factor carboxylation
  99. Front
    Clean summary of lipid-soluble vitamins
    Back
    Vitamin A is retinol, retinal, and retinoic acid for vision, epithelial function, and gene regulation; vitamin D is a cholesterol-derived hormone for calcium and phosphate and bone metabolism; vitamin E is an antioxidant with α-tocopherol most active; vitamin K exists as K1 and K2 and is required for γ-carboxylation of clotting proteins
  100. Front
    TAG versus phospholipid
    Back
    Triacylglycerol is glycerol plus 3 fatty acids with no phosphate, whereas a phospholipid is glycerol plus 2 fatty acids plus phosphate plus a head group
  101. Front
    PC versus PS
    Back
    Both are glycerophospholipids, but phosphatidylcholine has choline as head group whereas phosphatidylserine has serine as head group
  102. Front
    PC versus sphingomyelin
    Back
    Both can contain phosphocholine, but phosphatidylcholine has a glycerol backbone whereas sphingomyelin has a sphingosine or ceramide backbone
  103. Front
    Cholesterol versus phospholipid
    Back
    Cholesterol is a rigid sterol ring system, whereas phospholipids have long fatty acyl chains and a phosphate head group
  104. Front
    Super high-yield TAG fact
    Back
    Triacylglycerol is the major storage lipid and major dietary lipid
  105. Front
    Super high-yield phosphatidylcholine fact
    Back
    Phosphatidylcholine is lecithin
  106. Front
    Super high-yield membrane phospholipid fact
    Back
    Phosphatidylcholine is the major structural phospholipid of mammalian membranes
  107. Front
    Super high-yield phosphatidylserine fact
    Back
    Phosphatidylserine has a serine head group and a net negative charge
  108. Front
    Super high-yield sphingomyelin fact
    Back
    Sphingomyelin is built on sphingosine or ceramide, not glycerol
  109. Front
    Super high-yield cholesterol fact
    Back
    Cholesterol is a 4-ring sterol and stabilizes membranes
  110. Front
    Super high-yield cholesterol derivative fact
    Back
    Main cholesterol derivatives are bile acids, steroid hormones, and vitamin D
  111. Front
    Super high-yield fat-soluble vitamin fact
    Back
    Fat-soluble vitamins are A, D, E, and K and are transported in chylomicrons after absorption
  112. Front
    Super high-yield vitamin E fact
    Back
    Vitamin E is an antioxidant
  113. Front
    Super high-yield vitamin K fact
    Back
    Vitamin K is required for clotting factor carboxylation
  114. Front
    Cheat-sheet major lipid structures
    Back
    Triacylglycerol is glycerol plus 3 fatty acids; phosphatidylcholine (lecithin) is glycerol plus 2 fatty acids plus phosphate plus choline; phosphatidylserine is glycerol plus 2 fatty acids plus phosphate plus serine; sphingomyelin is ceramide plus phosphocholine; cholesterol is a rigid 4-ring sterol with an OH group
  115. Front
    Cheat-sheet lipid roles
    Back
    Triacylglycerol is for storage; phosphatidylcholine, phosphatidylserine, and sphingomyelin are membrane lipids; cholesterol provides membrane stability and is a precursor of bile acids, steroid hormones, and vitamin D
  116. Front
    Cheat-sheet lipid-soluble vitamins
    Back
    Vitamin A is for vision and epithelial function, vitamin D regulates calcium and phosphate, vitamin E is an antioxidant, and vitamin K is required for clotting factor carboxylation

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