Biochem 1

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Biochem 1
2011-12-12 18:54:46
Biochemistry Lipids

Biochem 1
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  1. What are 2 types of complex lipids
    • 1. Storage Lipids
    • 2. Structural Lipids
  2. What are some examples of storage lipids
    • 1. Acylglycerols
    • 2. Waxes
  3. What are some examples of structural lipids
    • 1. Glycerophospholipids
    • 2. Sphingolipids
  4. What are the 2 common properties of lipids
    • 1. Insolubility in aqueous or water-based solutions
    • 2. Solubility in oranic or non-polar solvents
  5. What are 5 biological functions of lipids
    • 1. Storage of energy
    • 2. Membrane structure
    • 3. Signaling molecules
    • 4. Cofactors for enzymes
    • 5. Antioxidants
  6. What is a non-essential function of lipids
  7. What are some examples of lipid pigmentation
    color of tomatoes, carrots, pumpkins and some birds
  8. How do lipids show color
    Compounds with long conjugated systems absorb light in the visible region of the spectrum
  9. How do lipids produce different colors?
    subtle difference in the chemistry of the compounds produce pigments of strikingly different colors.
  10. How do birds acquire pigments?
    Birds acquire the pigments that color thier feathers red or yellow by eating plant material containing carotenoid pigments
  11. What is canthaxanin?
    Bright red lipid pigment
  12. What is Zeaxanthin?
    Bright yellow colored lipid pigment
  13. Why do colors differ in male and female birds?
    The differences in pigmentation are the result of differences in intestinal uptake and processing of carotenoids.
  14. What is the major difference between complex lipids and biologically active lipids?
    Biologically active lipids have no fatty acids, whereas complex lipids do contain fatty acids
  15. What is the major difference between storage lipids and structural lipids?
    Storage lipids are on-polar, whereas structural lipids are polar lipids.
  16. What are some examples of biologically active lipids?
    • 1. Prostaglandins
    • 2. Steroids
  17. What is the structure of fatty acids at pH 7.0?
    At pH 7.0 fatty acids are fully ionized
  18. What is a common characteristic of almost all natural fatty acids?
    Almost all natural fatty acids have an even number of carbons.
  19. What is the pKa of COOH group?
  20. Are most natural fatty acids branched or un-branched?
    un-branched (hence the prefix -n)
  21. How do we commonly represent fatty acids?
    CH3-(R)n>2-COOH , where R= CH2
  22. What is the most common fatty acid chain length?
  23. What is Butanoic acid?
    • Four carbon fatty acid
    • Infinitely soluble in water, but solubility decreases with increased hydrocarbon chain length
  24. What is Lauric acid?
    • Twelve carbon ftty acid
    • Partially soluble in water to the extent of 006g/ gram of water
  25. Characteristics of fatty acids with C10 or higher saturated hydrocarbon chains
    Form waxy solids at room temperature
  26. Characteristics of C9 or lower saturated or unsaturated hydrocarbon chains
    Form oily liquids at room temperature
  27. Effects of double bonds in fatty acid chains
    Saturated fatty acids are more packed than un-saturated fatty acids
  28. Characteristics of ordered packing of fatty acids
    LESS ordered packing leads to WEAKER inter-molecular interactions
  29. Melting point of saturated vs un-saturated fatty acids
    un-saturated fatty acids have lower melting points
  30. Effects of chain length on solubility of fatty acids
    Solubility decreases as the chain length increases
  31. Effects of chain length on melting point of fatty acids
    Melting point increases as the chain length increases
  32. Factors that effect solubility and melting point
    • 1. Length of hydrocarbon chain
    • 2. Degree of Saturation
  33. How do doube bonds affect the shape of hydrocarbons?
    double bonds restrict rotation and introduct a rigid bend in the hydrocarbon tail. All other bonds in the chain are free to rotate
  34. How are Trans fatty acids formed?
    Trans fatty acids are formed by partial hydrogenation of unsaturated fatty acids and cis-double bond Isomerization to Trans-double bonds/
  35. How does a trans-double bond affect the shape of a fatty acid?
    Trans double bond allows a given fatty acid to adopt an extended conformatio
  36. How does a trans-double bond affect the melting point of a fatty acid?
    Trans fatty acids can pack more regularly and show higher melting points than is forms
  37. How do saturated and trans fats raise cholestrol?
    Saturated fatty acids increase blood cholesterol levels by providing proper packing domains for cholesterol. Trans fats also have increased rigidity around the double bond.
  38. Why is there a correlation between High Cholesterol and higher incidence of heart diseases?
    • Reduced membrane Fluidity
    • Reduced membrane Flexibility
    • Reduced membrane protein Function
  39. What is Anandamide
    A fatty acid derivative. Part of the fatty acid signalling molecules
  40. Where is Anandamide found?
    Found in the brain and in chocolate
  41. How is Anandamide similar to Marijuana?
    Anandamide turns on the same receptor as Marijuana
  42. How are Glycerol and Fatty acids linked in Acylglycerols?
    Linked by an Ester linkage
  43. Are tri-acylglycerols soluble or insoluble?
    Both animal and plat tri-acylglycerols are preset as insoluble forms
  44. Are animal tri-acylglycerols solid or liquid at room temperature?
    Animal triglycerides are solid at room temperature
  45. Are plant and fish tri-acylglycerides solid or liquid at room temperature?
    Pant and fish trigkycerides are oil at room temperature.
  46. How do fat and oil triglycerides differ?
    Degree of un-saturation
  47. What are simple tri-acylglycerols?
    All of the fatty acids are of the same length
  48. What are Mixed or Complex tri-acylglycerols?
    all three fatty acids are of different lengths and saturation
  49. How are tri-acylglycerols digested?
    Tri-acylglycerols are digested in the small intestine by the enzyme pancreatic lipase
  50. What are the advatage of fats over polysaccharides?
    Fatty acids carry less water along because they are non-polar
  51. Energy in Glucose and glycogen
    Glucose and glycogen are short-term energy needs, quick delivery
  52. Energy of Acylglycerides
    Acylglycerides are long term (months) energy needs, good storage, slow delivery
  53. How do tri-acylgycerols react with strong acids or bases?
    Leads to the hydrolysis of the Ester bond between glcyerol and fatty acids
  54. Reaction of tri-acylglycerol in a strong acid
    Tri-acylglycerol + 3H2O in strong acid --> Glycerol + Fatty-COO- H+
  55. Reaction of hard salt tri-acylglycerol to hard soap bars
    Tri-acylglycerol + 3NaOH --> Glycerol + Fatty salt-COO- Na+
  56. Reaction of soft salt to hand soap and shaving cream
    Tri-acylglycerol + 3KOH --> Glycerol + Fatty salt-COO- K+
  57. How are waxes formed?
    Waxes are formed by a condesnation reaction betwee long fatty acids and alcohol hydrocarbon chains
  58. What is the melting point range of waxes?
    60-100C, higher than tri-acylglycerols
  59. Do waxes contain glycerol?
  60. How are waxes broken down?
    Waxes are broken down with strong acids and bases to fatty acids and alcohol hydrocarbons
  61. What are the major components of cell membranes?
    Phospholipids, phospho-acylglycerols or Glycerophospholipids
  62. What is a property of Phosphatidic acids at pH 7
    Phosphatidic acids are negatively charged at pH 7
  63. What is phosphatidic acid?
    Phosphatidic acid is the base unit of phospho-acylglycerol and is made up of 1,2-diacylglycerol (two fatty acids plus glycerol) linked to phosphoric acid
  64. What are alcohol based compounds linked to phosphatidic acids known as?
    Head Groups
  65. What are Phospholipids made up of?
    Phospholipids are made up of phosphatidic acid or diacylglycerols linked to a head-group alcohol through a phospho-ester link
  66. All Phospho-acylglycerols have the same __________ but NOT ________
    • amphipathic property
    • net charge
  67. If the polar head-group is ethanolamine, what is the glycerophospholipid?
    Phosphatidyl ethanolamine
  68. What is Glycerol 3-phosphate?
    The backbone of phospholipids
  69. How do head groups effect the properties of membranes?
    ´╗┐The properties of head groups determine the surface properties of membranes?
  70. What is the major component of most eukariotic cell membranes?
  71. What charge do most eykariotic cell membranes have?
    Net charge of 0
  72. What is the major component of all cell membrane lipids?
  73. What is the general structure of glycerophospholipids?
    Contain phosphate groiup on C3 and two fatty acids on C1 and C2 of the glycerol backbone
  74. What determines the type and net charge of the glycerophospholipid?
    The head-group alcohol
  75. How is the had group linked to the glycerol backbone?
    Through a phosphodiester linkage
  76. What gives cell membranes their overall surface charges?
    The differential distribution of glycerophospholipids
  77. What is the backbone of sphingolipids?
    A long-chain amino alcohol: sphingosine
  78. How is a fatty acid attached to sphingosine?
    via an amide linkage
  79. What is produced by the joining of one fatty acid to sphingosine?
    Ceramide: very similar to diacylglycerol structurally
  80. What are the three classes of sphingolipids, and how are they determined?
    • Determined by head-group substitution
    • sphingomyelin
    • cerbroside
    • ganglioside
  81. What is produced by the addition of phosphoryl choline grup to sphingosine?
  82. What is produced y the addition of sugar group to sphingosine?
  83. What is produced by the addition of combination of sugars to sphingosine?
  84. What is attached to carbon 1 od a sphingosine?
    a polar head group
  85. How is the polar head group connected to carbon 1?
    By a glycosidic or phosphodiester linkage
  86. Where are sphingolipids mostly found?
    Sphingolipids localize to the OUTER leaflet of the cell membrane?
  87. In sphingosine, what is attached to the second animo group?
    a fatty acid in amide linkage
  88. Is the fatty acid in sphingosine saturated or unsaturated?
    The fatty acid is usually saturated or monounsatured with 16, 18, 22, or 24 carbon atoms
  89. How are blood groups determined?
    by the type of sugars located on the head groups in glycosphingolipids
  90. How is the structure of sugar determined?
    It is determined by an expression of specific glycosyltransferases
  91. What produces the O antigen on a glycosphingolipid?
    individuals with inactive glycosultransferase
  92. What produces the A blood group?
    Individuals with a glycosultransferase that transfers an N-acetylgalactosamine group
  93. What produces a B blood group?
    Individuals with a glycosyltransferase that transfers a galactose group to phosphate
  94. Do biologically active lipids have a fatty acid or glycerol backbone?
    Biologically active lipids DO NOT contain fatty acids or glycerol backbone, but can be generated from fatty acids
  95. What is the major role of biologically active lipids?
    Play major physiologic roles by recruiting the activities of proteins and receptors
  96. Why are steroids important for digestion?
    They are found in bile salts and they act as fat solubilizers
  97. What are the 2 major classes of iologically active lipids?
    • Prostaglandins
    • Sterols
  98. How are prostaglandins generated?
    Generated through modification of fatty acids
  99. How are sterols generated?
    Generated from 2 carbon acids (acetate) and through modification of other sterols
  100. How do cells turnover their lipids?
    in Lysosomes with four phospholipases (or esterases)
  101. What are phospholipases used for?
    Phospholipases cleave ester linkages but not ethyl linkages as in sphingosine
  102. What does phospholipase A1 do?
    Cleaves C1 ester linked fatty acid
  103. What does phospholipase A2 do?
    cleaves C2 ester linked fatty acid
  104. What does Phospholipase C do?
    Cleaves C2 phosphoester linked phosphoric acid
  105. What does Phospholipase D do?
    cleaves phosphoester linked X or head groups
  106. What are the two classes of phospholipases?
    • Phospholipid
    • Borad substrate phospholipases
  107. Where is phosphatidylinosital 4,5-bisphophate found?
    Found on the intracellular side of the cell membrane
  108. How is phosphatidulinosital 4.5-bisphosphate important?
    Its hydrolysis serves an important intracellular signalling pathway (protein Kinase C pathway)
  109. What is PHorbol 12-myristate 13-acetate (PMA)?
    A diester of phorbol and a potent tumor proter that activates the signal transduction enzyme protein kinase C. The effects of TPA on PKC result from its similarity to one of the natural activators of classic PKC isoforms, diacylglycerol
  110. What are phorbol esters?
    Cancer promoting agents that utilize the protein kinase C pathway
  111. What are paracrin lipid hormones?
    Present in small amounts but play vital roles as signaling molecules between nearby cells
  112. What does enzymatic oxidation of arachidonic acid yield?
    • Prostaglandins
    • thromboxanes
    • leukotrienes
  113. What is arachidonic acid?
    the precursor of eicosanoids
  114. What is the general structure of prostaglandin E?
    C-8 and C-12 of arachidonate are joined to form the cahracteristic five-membered ring
  115. What is arachidonate?
    Arachidonic acid at pH 7
  116. What is the general structyre of thrombozane A2?
    The C-8 and C-12 are joined and an oxygen atom is added to frm the six-membered ring
  117. What is the general structure of Leukotriene A4?
    Has a series of of three conjugatd couble bonds
  118. What are NSAIDS?
    Nonsteroidal antiinflammatory drugs
  119. What is an example of NSAIDs and how do they work?
    • Aspirin and ibuprofen
    • Block the formation of prostaglandins and thrombozxanes from arachidonate by inhibiting the enzyme cyclooxygenase (prostaglandin H2 synthase)
  120. What is the building block of sterol lipids?
  121. What is the general structure of a sterol?
    • Steroid nucleus: four fused rings
    • Hydroxyl group (polar head) in the A-ring
    • Various non-polar side chains
  122. What is cholesterol?
    Cholesterol is a 'steroid' with hydrophibic tail int wo parts, rigid planar rings and flexible and branched hydrocarbon chain
  123. What is the hydrophilic part of cholesterol made up of?
    Hydroxyl group
  124. What does cholesterol do to the lower ends of the fatty acids hydrocarbon tails?
    Cholesterol prevents the close packing of the LOWER ends of the fatty acids hydrocarbon tails, thus DECREASING the melting point of the lipid bilayer
  125. What does cholesterol do to the upper ends of the fatty acids hydrocarbon tails?
    Cholesterol promotes tight packing of the UPPER ends of the fatty acids hydrocarbon tais, thus INCREASING the melting point of the lipid bilayer
  126. Why is cholesterol known as a fluidity buffer?
    Where it decreases the shaprness of liquid to crystalline curve
  127. What does cholesterols rigid structure do?
    Cholesterols rigid structure favours interaction with saturated or trans-fats, hence, these fats enhance cholesterol accuulation in membrane
  128. What happens to amphipathic structural lipids in aqueous solutions?
    • In aqueous solutions amphipathic structural lipids aggregate into three possible structures:
    • Lipid micelles
    • Lipid Bilayer
    • Liposomes
  129. What are lipid micelles?
    • Small spherical structures
    • Water is exxcluded from the interior
    • Free fatty acids and some detergents assume this conformation because of head to tail ratio less than 1
  130. What are lipid bilayers?
    • Sheet like structure with two monolayer
    • Water is excluded from the interior
    • Phosphoacylglycerides and sphingolipids favour this lipid aggregates because of the head to tail ratio is equal to 1
  131. What are liposomes?
    • Hollow sphere of lipid bilayer folded back onto itself
    • Aggregates enclos water, thus act as barriers between two environments
  132. What is the cell membrane?
    An essential structure required for the evolution of cells and requird for life
  133. Who and when was the fluid mosaic model of the cell membrane proposed?
    Proposed in 1972 by Singer and Nicolson
  134. What is the cell membran impermeable to?
    Impermeable to charged ions and large molecules
  135. What is the cell membrane permeable to?
    Permeable to hydrophobic molecules and neutral gases and water
  136. What are the three classes of membrane proteins?
    • Integral or intrinsic membrane proteins
    • Anchored membrane proteins
    • Peripheral or associated membrane proteins
  137. What are integral or intrinsic membrane proteins?
    • Proteins that transverse the lipid bilayer one or several times.
    • Such proteins are extractable from the cell membrane with detergets
  138. Are integral or intsinic membrane proteins extractable from the cell membrane?
    Yes, they are extractable with detergents
  139. What are anchored membrane proteins?
    Proteins that do NOT transferse the lipid bilayer entirely, but are linked covalently to fatty acids in the inner or outer leaflet of the cell membrane
  140. Are anchored membrane proteins extractable?
    Yes, they are extraceable from the cell membrane with detergent (inner leaflet) or with treamtment with phospholipases (outer leaflet)
  141. What are peripheral or associated membrane proteins?
    Proteins that do NOT transferse the lipid bilayer, but associate with transmembrane proteins or interact with lipid surface charges
  142. What is a hyrdopathy plot?
    Hydropathy index is plotted against residue number for two integral membrae proteins
  143. When predicting TM domains, what is the number of amino acids requiredd to transverse the lipid bilayer based on?
    Based on 0.15 nm distance between each amino acid in an alpha helix structure and the width of the lipid bilayer which is 4.5-5 nm, icluding the head groups
  144. When predicting TM domains, how do you find the hydropathy value?
    The hydropathy value for 27 amino acids from a table of amino acid hydrophobicity values
  145. When predicting TM domains, how are the hydropathy values used?
    The hydropathy values for a window of 27 amino acids is used to scan the entire amimo acid sequence of the protein, one amino acid at a time
  146. When predicting TM domains, how do you represent one transmembrane domain?
    A hydropathy plot is generated for a protein, and a hydrophobic peak is taken to represent one transmembrane domain
  147. What are uniport transporters?
    • Facilitated diffusion
    • Primary active transport
    • Ion channel
  148. What are co-transporters (either symporters or antiporters)?
    • Faciitated diffusion
    • Secondary Active transport
  149. What is primary active transport?
    The energy released by ATP hydrolysis drives solute movement against an electrochemical gradient
  150. What is secondary active transport?
    A gradient X (often Na+) has been established by primary active transport. Movement of X down its electrochemical gradient now provides the energy to drive cotransport of a second solute (S) against its electrochemical gradient