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QUIZ 7 > PDH & TCA > Flashcards

PDH & TCA Flashcards

1
Q

Where does TCA occur?

A

mitochondrial matrix

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2
Q

function of TCA cycle

A

oxidation of acetyl CoA & participation in biosynthetic reactions

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3
Q

oxidation of acetyl CoA

A

metabolism of amino acids, fatty acids, and carbohydrates into CO2 + H2O; accounts for 2/3 of total O2 consumption and ATP production

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4
Q

What biosynthetic reactions does TCA play a part in?

A

formation of glucose from carbon skeletons of AAs and provides building blocks for heme synthesis

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5
Q

How much ATP can be generated from aerobic glycolysis + TCA?

A

38

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6
Q

How much ATP can be generated from anaerobic glycolysis?

A

only 2; no TCA

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7
Q

CoA

A

carrier of acetyl

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8
Q

acetyl group

A

CH3-C=O

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9
Q

outer membrane of mitochondria

A

contains porins that permit free diffusion of small molecules

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10
Q

inner membrane of mitochondria

A

contains transport proteins that control passage of metabolites such as ATP, ADP, pyruvate, Ca++, and phosphate; also contains coenzymes for ETC

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11
Q

mitochondrial matrix

A

contains enzymes of TCA cycle; fatty acid oxidation enzymes, ribosomes

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12
Q

pyruvate dehydrogenase complex

A

multimolecular complex located in mitochondrial matrix

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13
Q

function of PDH complex

A

converts pyruvate into acetyl-CoA for the TCA cycle

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14
Q

component enzymes of PDH

A
  1. pyruvate decarboxylase (E1)
  2. dihydrolipoyl transacetylase (E2)
  3. dihydrolipoyl dehydrogenase (E3)
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15
Q

component coenzymes of PDH

A
  1. thiamine pyrophosphate
  2. lipoic acid
  3. coenzyme A (CoA)
  4. flavin adenine dinucleotide (FAD)
  5. nicotinamide adenine dinucleotide (NAD+)
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16
Q

thiamine pyrophosphate (TPP)

A

E1-bound

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17
Q

lipoic acid

A

E2-linked

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18
Q

coenzyme A

A

E2-substrate

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19
Q

FAD

A

E3-bound

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20
Q

NAD+

A

E3-substrate

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21
Q

key coenzyme in PDH

A

thiamine pyrophosphate

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22
Q

Beriberi

A

clinical manifestation of thiamine deficiency that affects high-energy requiring tissues in the CV and CNS

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23
Q

Beriberi risk factors

A

diet consisting largely of white rice and alcholism

24
Q

overall reaction of PDH

A

pyruvate + CoA + NAD+ –> acetyl-CoA + CO2 + NADH

25
Q

kinase effect on PDH

A

phosphorylates PDH, inactivating it

26
Q

What stimulates kinase to phosphorylate PDH?

A

increase in acetyl CoA/CoA ration or NADH/NAD+ ratio (more products)

27
Q

phosphatase effect on PDH

A

dephosphorylates PDH, activating it

28
Q

What stimulates phosphatase to dephosphorylate PDH?

A

increase in ADP/ATP ratio (also inhibits kinase)

29
Q

TCA cycle

A

acetyl CoA + oxaloacetate –> citrate –> isocitrate –> alpha-ketoglutarate –> succinyl-CoA –> succinate –> fumarate –> malate –> oxaloacetate

30
Q

acetyl CoA + oxaloacetate –> citrate

A

aldol condensation; H2O to CoA

31
Q

citrate –> isocitrate

A

isomerization

32
Q

isocitrate –> alpha-ketoglutarate

A

oxidation & decarboxylation; NAD+ to NADH + H+ and CO2

33
Q

alpha-ketoglutarate –> succinyl CoA

A

oxidation and decarboxylation; NAD+ to NADH + H+ and CO2

34
Q

succinyl-CoA –> succinate

A

cleavage of thioester; GDP to GTP and CoA

35
Q

succinate –> fumarate

A

oxidation; FAD to FADH2

36
Q

fumarate –> malate

A

hydration

37
Q

TCA cycle overall reaction

A

acetyl CoA + 3NAD+ + FAD + GDP + Pi + H2O –> 2 CO2 + 3NADH + FADH2 + GTP + 3H+ + CoA

38
Q

malate –> oxaloacetate

A

oxidation; NAD+ to NADH + H+

39
Q

How many electrons transferred during TCA?

A

4 total; three from reducing NAD+ to NADH and 1 from FAD to FADH2

40
Q

TCA products

A

2 CO2, 1 FADH2, 3NADH, and 1GTP

41
Q

each NADH can produce _ ATP

A

3; so 9 total each cycle

42
Q

each FADH2 can produce _ ATP

A

2

43
Q

TCA cycle is regulated by _

A

substrate availability, product inhibition, and competitive feedback inhibition by cycle intermediates

44
Q

substrate availability _ regulates citrate synthetase

A

positively; acetyl-CoA & oxaloacetate

45
Q

product availability _ regulates citrate synthetase

A

negatively; NADH

46
Q

cycle intermediates _ TCA cycle

A

inhibit

47
Q

positive allosteric regulators of TCA cycle

A

ADP & Ca++

48
Q

ADP

A

levels increase with muscular contraction, biosynthetic reactions; activates isocitrate dehydrogenase

49
Q

Ca++

A

activates PDH to make acetyl-CoA; activates isocitrate dehydrogenase & alpha-ketoglutarate dehydrogenase

50
Q

amphibolic

A

process that is both catabolic and anabolic –> the TCA cycle

51
Q

How is TCA cycle amphibolic?

A

catabolic: acetyl-CoA oxidation for ATP generation
anabolic: biosynthetic pathways use TCA intermediates

52
Q

malate

A

transported out of mitochondria and converted to oxaloacetate for gluconeogenesis

53
Q

citrate

A

citrate from citrate synthetase is exported to cytosol and converted back to acetyl-CoA for fatty acid and cholesterol biosynthesis

54
Q

alpha-ketoglutarate

A

used to make glutamate

55
Q

succinyl-CoA

A

starting material for porphyrin (heme) biosynthesis

QUIZ 7 (12 decks)

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