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Biochem > Chapter 27 > Flashcards

Chapter 27 Flashcards

1
Q

where are fatty acids stored?

A

adipose tissue

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2
Q

what are fatty acids stored as?

A

triacyclglycerols (TAG)

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3
Q

what are triacylglycerols?

A

fatty acids that are linked to glycerol with ester linkages

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4
Q

where is adipose tissue most prominent?

A

subcutaneous (below the skin) and visceral (around internal organs)

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5
Q

why do muscles store fatty acids?

A

for use in producing energy

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6
Q

what are the three ways in which fatty acid triacyclglycerols are accessible from adipose tissue?

A
  1. degradation of TAG to release fatty acids and glycerol into the blood for transport to energy-requiring tissues
  2. activation of the fatty acids and transport into the mitochondria for oxidation
  3. degradation of the fatty acids to acetyl CoA for processing by the citric acid cycle
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7
Q

where does fatty acid degradation occur?

A

the mitochondria

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8
Q

what’s the difference between the use of glucose and lipids in producing ATP?

A

glucose can produce energy without oxygen
fatty acids require oxygen to produce energy

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9
Q

how are triacylglycerols stored in adipocytes?

A

as a lipid droplet

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10
Q

what stimulates the breakdown of lipids (lipolysis)?

A

epinephrine and glucagon acting through 7TM receptors

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11
Q

what is lipolysis?

A

the breakdown of lipids

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12
Q

what role does Protein Kinase A play in the breakdown of lipids?

A

it phosphorylates perilipin

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13
Q

what is perilipin associated with in lipolysis?

A

the lipid droplet and hormone-sensitive lipase

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14
Q

what is fatty acid breakdown dependent on?

A

glucagon and epinephrine

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15
Q

what happens in lipolysis after PKA phosphorylates perilipin?

A

Perilipin is activated and activates ATGL

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16
Q

where are most stores of TAGs found?

A

fat cells

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17
Q

when TAG’s are broken down, where does Glycerol go?

A

glycerol is transported to the liver for glycolysis and gluconeogenesis

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18
Q

when TAG’s are broken down what happens to the fatty acids?

A

they are transported to tissues for fatty acid oxidation

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19
Q

what must happen to fatty acids before they are oxidized?

A

they must be linked to Coenzyme A

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20
Q

how is CoA attached to fatty acids?

A

by a sulfhydryl bond

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21
Q

what is the rate determining step of fatty acid oxidation?

A

the attachment of CoA to the fatty acid by a sulfhydryl bond (forming Acyl CoA)

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22
Q

how is the reaction of fatty acid to Acyl CoA made irreversible?

A

by the hydrolysis of PPi

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23
Q

what happens after the fatty acid is linked to CoA and activated?

A

it is transferred to carnitine

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24
Q

what does carnitine do to fatty acids?

A

it transports them into the mitochondria

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25
Q

what catalyzes the transfer of a fatty acid to carnitine?

A

carnitine acyltransferase I

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26
Q

what transports the acyl carnitine into the mitochondria?

A

a translocase

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27
Q

what does carnitine acyltransferase II do?

A

it transfers the fatty acid to CoA in the mitochondria

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28
Q

What are the four steps of fatty acid degradation (β-oxidation)?

A
  1. Oxidation (FAD)
  2. Hydration (H2O)
  3. Oxidation (NAD+)
  4. Thiolysis (CoA)
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29
Q

what are the products after one round of fatty acid degradation?

A

Acyl CoA (-2 Carbons) + Acetyl CoA

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30
Q

what is reduced in the first oxidation step of fatty acid degredation?

A

FAD is reduced to FADH2

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31
Q

what is reduced in the second oxidation of fatty acid degradation?

A

NAD is reduced to NADH

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32
Q

how many cycles does it take to completely degrade a fatty acid?

A

7 cycles

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33
Q

how many ATP does the overall β - oxidation reaction yield?

A

106 molecules of ATP

34
Q

what does it mean if a fatty acid is saturated?

A

it contains only single bonds on the carbon chain

35
Q

what does it mean if a fatty acid is unsaturated?

A

it contains single and double bonds on the carbon chain

36
Q

when are isomerase and reductase needed?

A

when a fatty acid contains an even number amount of double bonds

37
Q

when is just isomerase needed?

A

when a fatty acid contains one or an odd number of double bonds

38
Q

Can β - oxidation proceed in unsaturated fatty acids?

A

No. Isomerase (or isomerase and reductase) are needed to saturate it

39
Q

what does isomerase do to an unsaturated fatty acid?

A

it transfers the double bond from the cis to the trans position, to allow β-oxidation

40
Q

what do isomerase and reductase do to an unsaturated fatty acid?

A

isomerase converts the first double bond from cis to trans

reductase gets rid of the second double bond

41
Q

what do fatty acids with an odd number of carbons produce during the thiolysis reaction?

A

Propionyl CoA

42
Q

where does the newly generated Succinyl CoA go after Thiolysis of a fatty acid with an odd number of carbons ?

A

The Citric Acid Cycle

43
Q

what are the 3 types of ketone bodies?

A

acetoacetate

3-hydroxybutyrate

acetone

44
Q

where are ketone bodies synthesized?

A

in liver mitochondria

45
Q

where are ketone bodies secreted?

A

into the blood

46
Q

what happens when there is a build up of Acetyl CoA?

A

Acetyl CoA can be converted to ketone bodies

47
Q

what causes a build up of Acetyl CoA?

A

the slow down of the citric acid cycle

48
Q

what does acetoacetate in the blood indicate?

A

abundance of acetyl CoA subunits

49
Q

what does an abundance of acetyl CoA lead to?

A

decrease in lipolysis

50
Q

what might use acetoacetate over glucose?

A

normal fuels for respiration, heart muscle, and renal cortex

51
Q

what is a ketogenic diet?

A

a diet rich in fats and low in carbohydrates but with adequate proteins

52
Q

what can ketogenic diets lead to?

A

formation of substantial amounts of ketone bodies

53
Q

what do ketogenic diets do in children with epilepsy?

A

it helps reduce seizures in children suffering from drug-resistant epilepsy

54
Q

can fatty acids be converted into glucose?

A

no

55
Q

what happens when there is a decrease in oxaloacetate?

A

it slows down the Citric Acid Cycle

56
Q

why can acetyl CoA derived from fats not lead to the net synthesis of oxaloacetate or glucose?

A

because although two carbons enter the cycle when acetyl CoA condenses with oxaloacetate, two carbons are lost as CO2 before oxaloacetate is regenerated

57
Q

Pyruvate to Acetyl-CoA is a(n) ___ reaction

A

irreversible

58
Q

what can excess production of ketone bodies cause?

A

acidosis

59
Q

what is diabetic ketosis?

A

an overproduction of ketone bodies that occurs in patients with diabetes due to lack of insulin function

60
Q

what happens if insulin is absent or not working?

A

glucose cannot enter cells

energy must be derived from fats

fatty acid release from adipose tissue is enhanced

61
Q

why does acetyl CoA build up?

A

because the oxaloacetate, which can be generated from glucose, is not available to replenish the citric acid cycle

62
Q

what happens when all energy must be derived from fats?

A

it leads to the production of acetyl CoA

63
Q

why isn’t glucose utilized much when insulin is absent?

A

insulin isn’t there to turn on glucose pathways

64
Q

what is the predominant fuel for the brain?

A

Glucose

65
Q

what happens at the beginning of starvation?

A

protein degradation is initially the source of carbons for gluconeogenesis in the liver

the glucose is released into the blood for the brain to use

66
Q

what happens after several days of fasting?

A

the brain starts to use ketone bodies as a fuel

67
Q

why are ketone bodies a better energy source than protein degradation during starvation?

A

ketone body use stops protein degradation and prevents tissue failure

ketone bodies are synthesized from fats, the largest energy store in the body

68
Q

what are ketone bodies synthesized from?

A

fats, the largest energy store in the body

69
Q

why aren’t amino acids a good source of energy?

A

using amino acids as an energy source causes the degradation of proteins which can cause organ failure

70
Q

what happens during starvation when ketone bodies begin to run out?

A

protein degradation starts

71
Q

why does protein degradation happen at the beginning of starvation?

A

the body needs time to build ketone body levels

72
Q

what is GLUT4?

A

glucose transporter for adipose tissue and muscle

insulin dependent

73
Q

what regulates GLUT4?

A

insulin

74
Q

what happens to GLUT4 when glucose is low?

A

GLUT4 doesn’t get induced

75
Q

what is GLUT2?

A

glucose transporter in liver

low affinity, high capacity

76
Q

where does acetyl CoA go to get oxidized?

A
77
Q

how many grams of glucose are needed per day for brain survival during starvation?

A

40 grams

78
Q

how many grams of glucose are needed normally for brain survival?

A

120 grams

79
Q

what is survival dependent on?

A

survival is time dependent on triacylglycerol amount

80
Q

what happens after lipid stores are gone and proteins are used for energy again?

A

death imminent

81
Q

what is the sparing effect?

A

ketone levels increase as days of starvation increase

glucose levels decrease as days of starvation increases

Biochem (12 decks)

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