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Biochemistry Post Midterm > Lipid Metabolism and Catabolism Ketone Body Synthesis and Utilization > Flashcards

Lipid Metabolism and Catabolism Ketone Body Synthesis and Utilization Flashcards

1
Q

why can’t glycerol formed in the adipose tissue not be reused in the adipose tissue?

A

adipose tissue lacks glycerokinase

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2
Q

what does glycerol enter once it it enters the liver?

A

glycolysis
gluconeogenesis
TAG synthesis

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3
Q

What is the storage form of lipid?

A

TAG

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4
Q

where and how is TAG stored?

A

white adipose tissue as lipid droplets

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5
Q

when are fatty acids in the TAG released as free fatty acids?

A

energy deficient state - FASTING

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6
Q

What enzyme breaks down TAGS?

A

hormone sensitive (HS) lipase

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7
Q

which state is HS lipase active? What activates it?

A

phosphorylated state
low insulin/glucagon ratio
fasting, flight, fight
- epinephrine stimulated via cAMP

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8
Q

what are the free fatty acids from adipose tissue bound to in blood?

A

albumin

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9
Q

which is NOT an important fuel source for the brain during starvation?

A

free fatty acids (not oxidized for energy by the brain)

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10
Q

what is beta oxidation?

A

oxidation of fatty acids at the beta carbon of the fatty acid

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11
Q

where does beta oxidation take place?

A

mitochondria

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12
Q

What are the stages of beta oxidation?

A

activation of fatty acid (cytosol)
transport of fatty acid from the cytosol to mitochondria
beta oxidation proper (reactions of beta oxidation)

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13
Q

what inhibits CPT-i?

A

malonyl CoA (when fatty acid synthesis is active, beta oxidation is inhibited)

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14
Q

what does one sequence of reactions of beta oxidation result in?

A

the cleavage of 2 C atoms (removed as acetyl CoA)

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15
Q

where are fatty acids used for beta oxidation and energy metabolism especially?

A

heart
skeletal muscle
liver

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16
Q

what fatty acids pass BBB to give energy to brain?

A

omega 3 and 6 only! - free fatty acids cannot pass

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17
Q

how are fatty acids activated? What is formed?

A

fatty acyl CoA synthetase (thiokinase)

forms fatty acyl CoA

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18
Q

whats the purpose of the carnitine shuttle?

A

transport long chain (16 - 20 C) fatty acyl groups into the mitochondria for beta oxidation

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19
Q

do medium chain fatty acids need a shuttle?

A

no, they enter directly into the mitochondrial matrix where they are activated to medium chain fatty acyl CoA for beta oxidation

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20
Q

where is CPT-I found? What are its substrates? What is the product?

A

outer mitochondrial membrane
fatty acyl CoA and free carnitine
forms fatty acyl carnitine

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21
Q

when is the carnitine shuttle activated?

A

when there is increased availability of cytosolic fatty acids during fasting

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22
Q

when fatty acid synthesis is taking place, what is inhibited?

A

carnitine shuttle

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23
Q

what inhibits CPT-I?

A

malonyl-CoA

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24
Q

when is malonyl-CoA formed?

A

in liver cytosol during fatty acid synthesis

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25
Q

what is deficiency of CPT-I due to? What are the symptoms?

A

rare, due to deficiency of the isozyme found in the liver

leads to severe hypoglycemia and hypoketonemia

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26
Q

What is deficiency of CPT-II due to? What are the symptoms?

A

affects the isozyme of the muscles

leads to cardiomyopathy and muscle weakness

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27
Q

what happens to TAGs in CPT-II deficiency?

A

TAGS accumulate in skeletal muscle and prolonged exercise leads to myoglobinuria and elevated levels of CK-MM in blood

28
Q

where are the enzymes for beta oxidation present?

A

mitochondrial matrix

29
Q

what does a cell need in order to perform beta oxidation?

A

mitochondria and an active ETC and OP which reforms NAD+ and FAD needed as coenzymes for Beta oxidation

30
Q

oxygen deficiency leads to high levels of NADH, which does what?

A

inhibits beta oxidation

inhibits PDH and TCA cycle

31
Q

what does each spiral of Beta oxidation produce?

A

1 FADH2
1 NADH
1 acetyl CoA
1 fatty acyl CoA that is 2 C shorter

32
Q

how many equivalents of ATP are produced in beta oxidation?

A

5 ATP

33
Q

what does 1 round of the TCA cycle produce?

A

3 NADH
1 FADH2
1 GTP

34
Q

how many ATP equivalents are produced in 1 round of TCA?

A

12 ATP

35
Q

why is it significant that beta oxidation only cleaves 2 C from the fatty acyl CoA?

A

leaves a shorter fatty acyl CoA that can continue in more beta oxidation spirals

36
Q

how many ATP does the total degradation of palmitate generate?

A

129 ATP

37
Q

how many ATP are formed when glucose is subjected to aerobic glycolysis, PDH and TCA cycle?

A

38 ATP (using malate -aspartate shuttle)

38
Q

what does odd chain fatty acids produce in beta oxidation?

A

acetyl CoA
and
the last acyl CoA = propionyl CoA

39
Q

What is the significance of propionyl CoA?

A

only part of the fatty acid that can provide carbons for gluconeogenesis

40
Q

what does propionyl CoA carboxylase need as a cofactor?

A

biotin

41
Q

what does methylmalonyl CoA mutase need as a cofactor>

A

Vitamin B12

42
Q

what accumulates as a result of Refsum disease?

A

phytanate

43
Q

what is deficient in Refsum Disease?

A

deficiency of the peroxisomal phytanyl CoA alpha - hydroylase = defect in alpha oxidation

44
Q

what are the symptoms of Refsum disease?

A

visual defects
ataxia
polyneuropathy
skeletal manifestations

45
Q

is there a Tx for Refsum disease? What is it?

A

Yes, dietary restriction of branched chain fatty acids

46
Q

what is MCAD deficiency?

A

most common inherited autosomal recessive enzyme deficiency

decreased ability to oxidize fatty acids with 6-10C (medium chain)

47
Q

what are the symptoms of MCAD deficiency?

A

on fasting, the liver and muscles are not able to use fatty acids as an energy source
profound hypoglycemia!

48
Q

what are excreted in urine with MCAD deficiency?

A

medium chain acyl carnitines
dicarboxylic acids
presence of CK-MM and myoglobin in urine = skeletal muscle damage

49
Q

what leads to the inhibition of MCAD by hypoglycin A?

A

unripe ackee fruit - ONLY unripe!

Jamaican vomiting sickness

50
Q

what does Jamaican vomiting sickness inhibit and result in?

A

inhibits beta oxidation

results in profound hypoglycemia

51
Q

how much energy supply is from fatty acid oxidation on an overnight fast?

A

60-70%

52
Q

what are common features of systemic fatty acids oxidation disorders? (MCAD, carnitine deficiency, CPT deficiency)

A

hypoglycemia

hypoketosis

53
Q

what accumulates in Zellweger syndrome and why?

A

very long chain fatty acids accumulate

cannot be degraded because lack of peroxisomes

54
Q

what are the clinical manefestations of Zellweger syndrome?

A

neurological manifestations (mental retardation)
hepatomegaly
fatal in infancy!

55
Q

how is ketone bodies in liver made?

A

acetyl CoA from fatty acid oxidation are converted to ketone bodies - peripheral tissues cannot synthesize ketone bodies

56
Q

what are the three ketone bodies?

A

acetoacetate
3-hydroxybutyrate (beta hydroxybutyrate)
acetone

57
Q

which ketone bodies are transported to peripheral tissues? What happens to them there?

A

acetoacetate and 3-hydroxybutyrate

reconverted to acetyl CoA - that are oxidized by TCA cycle!

58
Q

what organ synthesizes ketone bodies? why?

A

liver

contains lots of mitochondrial HMG CoA synthase

59
Q

what is exhaled and smelt on breath of DM type I patients?

A

acetone

60
Q

when does the liver synthesize ketone bodies?

A

during fasting, fight or flight situations

61
Q

where does ketogenesis take place?

A

mitochondria

62
Q

when is 3-hydroxybutyrate formed?

A

when ratio of NADH / NAd+ is increased - when Beta oxidation is predominant

63
Q

what does the brain use in addition to glucose during prolonged starvation?

A

ketone bodies

64
Q

What is the ‘protein sparing effect of ketone bodies’?

A

Ketonebodies can be used by the brain during fasting –this adaptation spares the breakdown of muscle protein (amino acids) for gluconeogenesis

65
Q

what does the brain use in addition to glucose during prolonged starvation?

A

ketone bodies

66
Q

What is the ‘protein sparing effect of ketone bodies’?

A

Ketonebodies can be used by the brain during fasting –this adaptation spares the breakdown of muscle protein (amino acids) for gluconeogenesis

Biochemistry Post Midterm (24 decks)

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