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Flashcards

Lipid metabolism

Hannah Tribe MCBHD Degree English 51 cards

Cards in this deck (51)

  1. 1Give 4 functions of lipids in the body1. cell membranes
    2. uptake of lipid soluble vitamins
    3. precursors to steroid hormones
    4. energy store
  2. 2Fat has a much higher _____ _________ than carbohydrates or proteinsenergy content
  3. 3When _________ ________ exceeds __________, excess is laid down as fat.calorific intake,
    consumption
  4. 4Which tissue uses fat as their preferred energy source?Cardiac muscle
  5. 5Triglycerides are ______ fats consisting of a ________ molecule which 3 _______ _______ attached. It is a concentrated store of energy.neutral,
    glycerol,
    fatty acids
  6. 6What are fatty acids?Chains of methyl groups with a terminal carboxyl group
  7. 7_________ fatty acids must be obtained from the dietessential
  8. 8Humans cannot create double bonds in fatty acids less than position ___9
  9. 9Name 2 places where fatty acid synthesis can take place?1. Hepatocytes
    2. Adipocytes
  10. 10Where in the cell does fatty acid synthesis take place?Cytosol
  11. 11What are 3 substrates needed in fatty acid synthesis?1. Acetyl CoA
    2. NADPH
    3. ATP
  12. 12How is citrate formed?Combining Acetyl CoA with oxaloacetic acid in the TCA cycle
  13. 13How is the Acetyl CoA transported from the mitochondria to the cytosol for fatty acid synthesis?Citrate-malate antiporter
  14. 14What is its mechanism?INSIDE MITOCHONDRIA: Acetyl CoA + Oxaloacetic acid = Citrate.
    Citrate transported across membrane into cytosol, to be split into Acetyl CoA and Oxaloacetic acid again. Oxaloacetate converted to Malate (using NADH) then to Pyruvate (releasing NADPH) which is transported back across the membrane to be converted to oxaloacetate and begin the cycle again.
  15. 15How is this transfer mechanism helpful?It has produced 2 of the substrates needed for fatty acid synthesis - Acetyl CoA and NADPH
  16. 16Where else can NADPH be obtained from?Pentose phosphate pathway
  17. 17What is the first step in fatty acid synthesis?Acetyl CoA + ATP + HCO3- ---> Malonyl CoA + ADP + Pi
  18. 18Which enzyme catalyses this reaction?Acetyl CoA carboxylase
  19. 19What stimulates and inhibits this reaction?stimulated by: citrate
    inhibited by: palmitate (fatty acid)
  20. 20Which vitamin is required for this reaction?Biotin
  21. 21What must Malonyl-CoA and Acetyl CoA bind to in order to be activated?ACP - acyl carrier protein
  22. 22Acetyl-ACP and Malonyl-ACP combine in a __________ reaction to give ________-____ (4C), releasing _____.condensation,
    acetoacetyl-ACP,
    CO2
  23. 23Acetoacetyl-ACP undergoes a ________ reaction, then a __________ reaction, then another _________ reaction. The product is ________-____ and 2 molecules of _______ are used.reduction,
    dehydration,
    reduction,
    butyryl-ACP,
    NADPH
  24. 24Butyryl-ACP combines with another _______-___ molecule to elongate the chain of fatty acids.Malonyl-ACP
  25. 25All the enzymes required in the elongation of the fatty acid chains form a complex called _____ _____ ________.fatty acid synthase
  26. 26Fatty acid synthase exists as a dimer. What does this mean?Two molecules joined together. They exist in a head-to tail formation
  27. 27Cholesterol is ________ and virtually ________ in water. It is the precursor of _______, ______ and _____ ______.hydrophobic,
    insoluble,
    sterols,
    steroids,
    bile salts
  28. 28How is cholesterol transported in circulation?As cholesteryl esters
  29. 29Where in the body is cholesterol synthesised?mostly in the liver, but also in adrenal cortex
  30. 30Where in the cell is cholesterol mostly synthesised?ER
  31. 31Synthesis of cholesterol is a complex process with many steps. What is the main regulatory step?Conversion of HMGCoA to mevalonate, using HMGCoA reductase enzyme
  32. 32What inhibits that enzyme and thus synthesis of cholesterol?Cholesterol
  33. 33Therefore why is it difficult to reduce circulating cholesterol levels by diet alone?Low levels of cholesterol stimulate its synthesis
  34. 34What are the 3 key steps in releasing energy from fat stores, and where do they take place?1. Mobilisation (from adipocyte)
    2. Activation (in liver cytosol)
    3. Degradation (in liver mitochondria)
  35. 35What happens during mobilisation?A hormone (often glucagon) stimulates the Gs pathway to produce cAMP and PKA. PKA phosphorylates the enzyme triacylglycerol lipase, thus activating it. This breaks triacylglycerol to diacylglycerol. Other lipases break this down to glycerol and free fatty acids.
  36. 36What happens to the glycerol?It is absorbed by the liver, and converted in a series of reactions into glyceraldehyde 3 phosphate , which can enter glycolysis or gluconeogenesis.
  37. 37What happens to the free fatty acids?taken back to the liver OR resynthesised into triglycerides
  38. 38In the liver cytoplasm, free fatty acids are activated by _____ to form ______ ______ ____. This is combined with ________ using the enzyme __ __ __ __, to give _____ _____ ________.CoA,
    fatty acyl CoA,
    carnitine,
    CATI,
    fatty acyl carnitine
  39. 39The _____ _____ ________ is transported into the matrix of the mitochondria in the liver by _________. In the matrix, __ __ __ __ enzyme converts ______ ______ _________ back into _____ ______ ___ and _________. This transfer process is only needed for longer chain FA.fatty acyl carnitine,
    translocase,
    CATII,
    fatty acyl carnitine,
    fatty acyl CoA,
    carnitine
  40. 40Once inside the matrix, _______ ____ undergoes __ __________. This process removes __ carbon units and produces _________ ____ , _____ and _____, by a series of reactions.Acyl-CoA,
    beta-oxidation,
    2,
    Acetyl CoA,
    FADH2,
    NADH
  41. 41What is the fate of the FADH2 and NADH produced from beta oxidation?Used to generate ATP
  42. 42If there is carbohydrate metabolism also occuring, the ______ ____ produced will enter the ____ ______. However usually if ______ ________ of ______ _____ is taking place, there is little glucose available, so the _____ _______ is not taking place - _________________ is instead making glucose. This process uses _____________ and so _______ ____ builds up and is instead converted to ________ _______.Acetyl CoA,
    TCA cycle,
    beta oxidation,
    fatty acids,
    TCA cycle,
    gluconeogenesis,
    oxaloacetate,
    acetyl CoA,
    ketone bodies
  43. 43What are the 3 ketone bodies?1. Acetoacetate
    2. 3 beta hydroxybuterate
    3. Acetone
  44. 44Acetyl CoA is converted to acetoacetate in 3 stages: 1. Acetyl CoA --> _________ ____ 2. ________ ____ --> __ __ __ ____ 3. __ __ __ ____ --> Acetoacetateacetoacetyl-CoA,
    acetoacetyl-CoA,
    HMG-CoA,
    HMG-CoA
  45. 45Acetoacetate can then be reduced to give the other ketone bodies: __ __ _____________ _____ and ________.3 beta hydroxybutyric acid,
    acetone
  46. 46What causes the sweet fruity smell of people's breath who have ketosis?Acetone
  47. 47Who may be particularly susceptible to this?Uncontrolled type 1 diabetics, or people on a low/no carb diet
  48. 48Which tissues use ketone bodies as a source of energy?Cardiac muscle and kidneys
  49. 49Which tissue will use ketone bodies for energy during times of starving?Brain
  50. 50What are 4 effects of insulin in response to high levels of glucose?1. Increased glycolysis in liver
    2. Increased fatty acid synthesis in liver
    3. Increased triglycerides in adipocytes
    4. Decreased beta oxidation
  51. 51What 2 substances stimulate mobilisation of triglycerides in adipose tissue?1. Glucagon
    2. Adrenaline

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Degree MCBHD Flashcards on Lipid metabolism, created by Hannah Tribe on 30/04/2014.
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Hannah Tribe
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