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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
what is deficiency of CPT-I due to? What are the symptoms?
rare, due to deficiency of the isozyme found in the liver | leads to severe hypoglycemia and hypoketonemia
26
What is deficiency of CPT-II due to? What are the symptoms?
affects the isozyme of the muscles | leads to cardiomyopathy and muscle weakness
27
what happens to TAGs in CPT-II deficiency?
TAGS accumulate in skeletal muscle and prolonged exercise leads to myoglobinuria and elevated levels of CK-MM in blood
28
where are the enzymes for beta oxidation present?
mitochondrial matrix
29
what does a cell need in order to perform beta oxidation?
mitochondria and an active ETC and OP which reforms NAD+ and FAD needed as coenzymes for Beta oxidation
30
oxygen deficiency leads to high levels of NADH, which does what?
inhibits beta oxidation | inhibits PDH and TCA cycle
31
what does each spiral of Beta oxidation produce?
1 FADH2 1 NADH 1 acetyl CoA 1 fatty acyl CoA that is 2 C shorter
32
how many equivalents of ATP are produced in beta oxidation?
5 ATP
33
what does 1 round of the TCA cycle produce?
3 NADH 1 FADH2 1 GTP
34
how many ATP equivalents are produced in 1 round of TCA?
12 ATP
35
why is it significant that beta oxidation only cleaves 2 C from the fatty acyl CoA?
leaves a shorter fatty acyl CoA that can continue in more beta oxidation spirals
36
how many ATP does the total degradation of palmitate generate?
129 ATP
37
how many ATP are formed when glucose is subjected to aerobic glycolysis, PDH and TCA cycle?
38 ATP (using malate -aspartate shuttle)
38
what does odd chain fatty acids produce in beta oxidation?
acetyl CoA and the last acyl CoA = propionyl CoA
39
What is the significance of propionyl CoA?
only part of the fatty acid that can provide carbons for gluconeogenesis
40
what does propionyl CoA carboxylase need as a cofactor?
biotin
41
what does methylmalonyl CoA mutase need as a cofactor>
Vitamin B12
42
what accumulates as a result of Refsum disease?
phytanate
43
what is deficient in Refsum Disease?
deficiency of the peroxisomal phytanyl CoA alpha - hydroylase = defect in alpha oxidation
44
what are the symptoms of Refsum disease?
visual defects ataxia polyneuropathy skeletal manifestations
45
is there a Tx for Refsum disease? What is it?
Yes, dietary restriction of branched chain fatty acids
46
what is MCAD deficiency?
most common inherited autosomal recessive enzyme deficiency | decreased ability to oxidize fatty acids with 6-10C (medium chain)
47
what are the symptoms of MCAD deficiency?
on fasting, the liver and muscles are not able to use fatty acids as an energy source profound hypoglycemia!
48
what are excreted in urine with MCAD deficiency?
medium chain acyl carnitines dicarboxylic acids presence of CK-MM and myoglobin in urine = skeletal muscle damage
49
what leads to the inhibition of MCAD by hypoglycin A?
unripe ackee fruit - ONLY unripe! | Jamaican vomiting sickness
50
what does Jamaican vomiting sickness inhibit and result in?
inhibits beta oxidation | results in profound hypoglycemia
51
how much energy supply is from fatty acid oxidation on an overnight fast?
60-70%
52
what are common features of systemic fatty acids oxidation disorders? (MCAD, carnitine deficiency, CPT deficiency)
hypoglycemia | hypoketosis
53
what accumulates in Zellweger syndrome and why?
very long chain fatty acids accumulate | cannot be degraded because lack of peroxisomes
54
what are the clinical manefestations of Zellweger syndrome?
neurological manifestations (mental retardation) hepatomegaly fatal in infancy!
55
how is ketone bodies in liver made?
acetyl CoA from fatty acid oxidation are converted to ketone bodies - peripheral tissues cannot synthesize ketone bodies
56
what are the three ketone bodies?
acetoacetate 3-hydroxybutyrate (beta hydroxybutyrate) acetone
57
which ketone bodies are transported to peripheral tissues? What happens to them there?
acetoacetate and 3-hydroxybutyrate reconverted to acetyl CoA - that are oxidized by TCA cycle!
58
what organ synthesizes ketone bodies? why?
liver | contains lots of mitochondrial HMG CoA synthase
59
what is exhaled and smelt on breath of DM type I patients?
acetone
60
when does the liver synthesize ketone bodies?
during fasting, fight or flight situations
61
where does ketogenesis take place?
mitochondria
62
when is 3-hydroxybutyrate formed?
when ratio of NADH / NAd+ is increased - when Beta oxidation is predominant
63
what does the brain use in addition to glucose during prolonged starvation?
ketone bodies
64
What is the 'protein sparing effect of ketone bodies'?
Ketonebodies can be used by the brain during fasting –this adaptation spares the breakdown of muscle protein (amino acids) for gluconeogenesis
65
what does the brain use in addition to glucose during prolonged starvation?
ketone bodies
66
What is the 'protein sparing effect of ketone bodies'?
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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