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Flashcards in Khan Fatty Acid Oxidation Deck (58):
1

34. Are fatty acids a source of energy for all tissues?

No

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35. How much energy does oxidation of fat yield?

9kcal/g

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36. What are fats largely ingested as?

TAG

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37. What pathway oxidizes FA?

B-Oxidation

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38. How are FA transported?

Bound to serum albumin

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39. What are some examples of saturated fA?

39. palmitate (16C), stearate (18C), arachidate (20C)

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40. What are some examples of monounsaturated FA?

40. palmitoleate, oleate (18C)

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41. What are some examples of polyunsaturated FA (PUFA)?

41. linoleic, linolenic, arachidonic

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42. What bond is cleaved in beta‐oxidation?

42. α‐β bond (by standard organic chemistry nomenclature convention)

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43. What FA can humans not synthesize, thus require in diet?

43. ω‐3,ω‐6

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44. Does glucagon stimulate FA synthesis?

44. no, it stimulates lipolysis

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45. Describe hepatic glycerol metabolism.

45. Gycerol kinase phosphorylates glycerol to glycerol 3 phosphateG3P DHGNG

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46. What two hormones increase cAMP levels and in turn lipolysis (via PKA actions on Hormone
sensitive lipase)?

46. Glucagon, Epi

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47. What is an antilipolytic hormone?

Insulin

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48. What can lack of insulin in Type 1 diabetes lead to ( in terms of FA metabolism)?

Keto Acidosis

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49. What are long chain FA’s carried on in the blood?

Serum Albumin

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50. How is a FA transported across the mitochondrial membrane?

50. Transport coupled to carnitine (which is mt. membrane soluble)

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51. What happens to FA in the mitochondria?

51. Oxidizing environment, NAD is high relative to NADHrx. Favoring reducing equivalents
favored and NADH/FADH2 produced for energy utilization via CAC,ETC, KB,etc.

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52. How are FA’s activated in order to form FA‐CoA

52. FA‐CoA synthetase claves ATP to AMP (2 high energy bonds) to produce FA‐CoA and
pyrophosphate (uses the energy from repulsion,entropy,resonance of ATP to form a high energy
thioester bond, energy is conserve)

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53. How many high energy phosphate bonds are required just for activation of FA to FA‐CoA?

2

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54. What nucleotide is cleaved to activate FA?

54. ATP to AMP.. if you miss this now you deserve to get it wrong

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55. What is the method of transport for short and medium chain FA’s into the mt.?

Diffusion

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56. What is the method of transport for long chain FA’s into the mt.?

Carnitine Transport

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57. Where are very long chain FA’s oxidized?

Peroxisome

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58. What are the enzymes that reversibly transport FA‐CoA and Fa‐Carnitine in the mt.?

58. Carnitine‐palmitoyl‐transferase 1 and 2 (CPT1,CPT2); CPT1 is on outer mt membrane, CPT2 is on inner membrane (reforms FA‐CoA and releases carnitine inside mt.)

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59. Is there a shuttle for FA‐CoA?

59. If there was, why are we talking about all this carnitine transport business

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60. What is the first step of β‐oxidation

60. AcylCoA DH takes 2e‐ out into FADH2 from saturated FA, oxidizes alpha‐beta carbon bond to
alkene

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61. What is the second step of β‐oxidation

61. Hydration via enoy CoA hydratase

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62. Describe the action of glucagon on lipolysis

62. Glucagon receptorGsACcAMP via ATPPKAhormone sensitive lipase and perilipins
phosphorylateddegradation of TAG

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63. What is the third step of β‐oxidation?

63. B‐hydroxyacylCoA DH , oxidizes hydroxyl to ketone & produces NADH

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64. What is the fourth step of β‐oxidation?

64. β‐ketothiolase (cleaves terminal Acyl‐CoA), reverse claisen condensation, thioester attached to
ketone of beta carbon is good for nucleophilic attack

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65. How many rounds of β‐oxidation to completely breakdown oleate?

8

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66. How many rounds of β‐oxidation to completely breakdown palmitate?

7

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67. What is similarity between CAC and β‐oxidation?

67. Hydration, and oxidation of metabolites to produce FADH2 and NADH

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68. Where is AcylCoA synthetase located?

68. Bound to outer mt. membrane

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69. Why can short and medium chain FA enter mt but not long chains?

69. ...large ones are biggercan’t diffuse..recall the pores acoss mt are membrane are selective for
size

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70. Why is the AcylCoA synthetase rx irreversible?

70. Entropy, imagine trying to rearrange PPi to ATP with so very few PPi’s present (cleavage of PPi
and the thioster bond is similar in free energy)

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71. How does free carnitine return across the membrane?

Translocase

39

72. What inhibits CPT1?

72. malonyl coA a FA synthesis precursor

40

73. What is the logic of CPT1/2?

73. FA’s are carried via O‐acyl carnitine linkages which have an eq. constant near 1, due to orbital
overlap bw C and O , usually this is not the case however it takes the place of the high energy due to thioeser bonds that have less overlap beteen S and C therefore less resonance stabilization and less energy than usual

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74. What is the regulated step of FA oxidation?

74. CPT1, entry into mt. recall cytosol and mt have diff. CoA pools (mt is used for ox, cyt. Is used for synthesiscompartmentalization once we move between pools we are more or less committed to the pathway).

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75. How are electrons transferred from FADH to ETC?

75. ETFCoQETC via a series of semiquinones,etc.

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76. How many ATP’s are generated by oxidation of a saturated 16 C FA?

76. 7FADH2x1.5,7NADHx2.5,8AcetylCoAx10,‐2ATP=106ATP

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77. How many ATP’s are generated by oxidation of a saturated 22 C FA?

148

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78. How many ATP’s are generated by oxidation of a saturated 49 C FA?

337

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79. How many ATP’s are generated by oxidation of a saturated 109 C FA?

757so how do I get these #? Use the formula 2(N‐2)+5N‐2 for any saturated FA where N = # of
carbons

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80. How many ATP’s are generated by oxidation of palmitate (d16:9)?

80. 102 (loss of first round and usage of NADPH)

48

81. What is the major control of FA oxidation?

Availability of FA

49

82. What enzyme does insulin stimulate in FA synthesis?

82. ACC (Acetyl CoA carboxylase)

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83. What is different in oxidation of unsaturated FA?

83. Isomerizes from cis unconjugated double bonds via enoylCoA isomerae to trans, ciscontinue
beta oxreduce conjugated double bond via 2,4 dienoyl CoA reductase (uses NADPH) and
produces trans d3 and is then isomerized into trans d2

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84. What is different in oxidation of odd chain FA?

84. Production of propionyl CoA upon terminal rx of beta oxpropionyl CoA carboxylase (uses
1ATP for AMP) to produce methylmalony CoA via an epimerasemutase to produce succinyl CoArun it through TCA for 1 GTP, 1 FADH2 and 1 NADH (basically lose 2NADH from AKG DH,isocitrate DH)

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85. What vitamin does methylmalonyl coa mutase require?

85. B12 (corrin ring structure)

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86. What is the 1st step of peroxisome oxidation of FA?

86. AcylCoa DH (makes FADH2 and peroxide)

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87. What step is diff. in peroxisomal oxidation of FA? How many times is oxidation repeated?

87. 1st step, until chain is 6‐10C’s ong and can be transported to mt. where oxidation is completed

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88. What type of oxidation is used in peroxisome? What disease is correlated with a defect in this?

88. Alpha oxidation, Refsun’s disease

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89. Where does omega‐oxidation take place?

ER

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90. What is the most common sort of deficiencies in FA oxidation?

90. Oxidation of MCAD’s: treatment is to avoid fasting, eat meals with less fat to control lipolysis
and decrease dependence on ketones

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91. What is the energy diff. in peroxisomal oxidation of FA?

91. Loss of energy from first step (still produces FADH but is not coupled to ETC since its not in mt,
transfers e‐ instead to peroxide)