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Biochemistry > TCA Cycle > Flashcards

TCA Cycle Flashcards

1
Q

What vitamin is succinate dehydrogenase derived from

A

Riboflavin

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2
Q

FAD and FMN are coenzymes for

A

Succinate dehydrogenase

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3
Q

What is a cofactor for pyruvate dehydrogenase

A

Thiamine pyrophosphate (B1)

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4
Q

What is the nicotinamide ring on NAD+?NADH derived from

A

Niacin B3

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5
Q

CoA is derived from

A

Pantothenic acid

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6
Q

Cofactor for pyruvate carboxylase

A

Biotin B7

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7
Q

What does pyruvate carboxylase do

A

Converts pyruvate to oxaloacetate when cycle is low on components

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8
Q

Pyruvate to acetyl CoA

A

Pyruvate dehydrogenase

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9
Q

Pyruvate to oxaloacetate

A

Pyruvate carboxylase

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10
Q

What enzyme is embedded in the mitochondrial membrane?

A

Succinate dehydrogenase

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11
Q

What complex is succinate dehydrogenase in

A

Complex II of ETC

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12
Q

What is the thioester bond in succinyl coA cleaved by

A

Succinate thiokinase

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13
Q

What is succinate thiokinase used for

A

Synthesis of high energy phosphate bond for GTP

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14
Q

What is in the a-keto acid dehydrogenase complex protein family

A

a-ketogluturate dehydrogenase complex
Pyruvate dehydrogenase complex
Branched chain amino acid dehydrogenase complex

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15
Q

Sources for acetyl coA

A

fatty acids (palmitate)
ketone body (acetoacetate)
Sugar (glucose)
Pyruvate
Alanine
Ethanol

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16
Q

E1

A

a-keto acid decarboxylase
Contains TPP
Cleaves off Co2

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17
Q

E2

A

Transacyclase containing lipoic acid
Transfers acyl of a-keto acid from thiamine–>CoASH–> produces acetyl coA

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18
Q

E3

A

Dihydrolipoyl dehydrogenase contains FAD—> reduces it to NAD+—> generates NADH

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19
Q

Succinate dehydrogenase is derived from

A

B2 Riboflavin

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20
Q

Pyruvate dehydrogenase and a-ketogluatare dehydrogenase contain

A

TPP B1

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21
Q

What happens to the lipoate on E2 in pyruvate dehydrogenase

A

It is reduced when it accepts the acyl group from E1

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22
Q

Which vitamins are necessary for decarboxylation of a-ketoglutarate

A

B1, 2, 3, 5

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23
Q

What is derived from coenzyme A

A

B5 pantothenic acid

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24
Q

Which enzyme involves TPP (B1)

A

a-ketoglutarate dehydrogenase

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25
Q

Lipoate is attached to what

A

e-amino group of lysine of transacylase enzyme

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26
Q

What form is transylase enzyme

A

E2

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27
Q

What happens to the oxidized lipoate disulfide form

A

Reduced, accepts acyl group from TPP

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28
Q

Arsenic poisioning

A

Lipoic acid is a target of arsenite inhibition due to binding of -SH groups

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29
Q

Which enzymes produce NAD+/NAH

A

Malate dehydrogenase, a-ketoglutarate, isocitrate dehydrogenase

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30
Q

What is a-ketoglutarate dehydrogenase derived from

A

TPP

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31
Q

Which part of the TCA is positive delta G

A

Citrate to isocitrate
Malate to OAA

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32
Q

What is citrate synthase controlled by

A

Concentration of AA, substrate, and citrate

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33
Q

What is citrate an inhibitor of

A

Product inhibitor, Its competitive with OAA

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34
Q

Isocitrate dehydrogenase is activated by ____ during muscular contraction

A

Ca++

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35
Q

Isocitrate dehydrogenase is allosterically activated by

A

ADP

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36
Q

Isocitrate dehydrogenase is inhibited by

A

NADH

37
Q

What is a-ketoglutarate dehydrogenase inhibited by

A

NADH, succinyl CoA, GTP

38
Q

What is a-ketoglutarate dehydrogenase activated by

A

Ca++

39
Q

Two functions of TCA cycle

A
  1. maintaining cellular ATP homeostases
  2. Regulating concentration of TCA cycle intermediates
40
Q

What happens when TCA intermediates are removed from cycle

A

Intermediates are depleted, less NADH and FADH2 for oxphos

41
Q

Intermediate for amino acid synthesis

A

OAA, a-ketoglutarate dehydrogenase

42
Q

Intermediate for Gluconeogenesis

A

Malate

43
Q

Intermediate for FA synthesis

A

Citrate

44
Q

Intermediate for Amino acid synthesis and neurotransmitter

A

a-ketoglutarate

45
Q

Intermediate for heme synthesis

A

Succinyl coA

46
Q

What happens if there is excess citrate

A

Gets split back into OAA and acetylCoA
Acetyl coa becomes FA which bundles into TG
TG gets stored for fat
Acetylcoa becomes cholesterol

47
Q

Major anaplerotic enzyme

A

Pyruvate carboxylase

48
Q

Pyruvate carboxylase is activated by

A

Acetyl CoA

49
Q

What reactions refill the cycle and produce TCA intermediates

A

Anaplerotic reactions

50
Q

What provides key substrates for anaplerotic pathways

A

Amino acids and odd chain fatty acids

51
Q

What are two major anaplerotic pathways

A
  1. Amino acids –> pyruvate –> OAA (generates ATP)
  2. Odd chain fatty acids –> valine, isoleucine –> propionyl CoA –> succinyl CoA
52
Q

Pathway from

A
53
Q

What does TCA produce

A

MOST of CO2
3 NADH
1 FADH 2H
1 OAA

54
Q

What does glycolysis produce

A

2 pyruvates yields 2 acetyl coa via pyruvate dehydrogenase complex

55
Q

What activates PDC active form

A

NAD+
Pyruvate

56
Q

What inactivates PDC

A

NADH
Acetyl CoA

57
Q

An accumulation of ADP and pyruvate does what to PDC

A

Inhibits PDC kinase, activates PDC

58
Q

An accumulation of NADH and acetyl coA does what to PDC

A

Activates PDC kinase, inactivates PDC

59
Q

An accumulation of calcium does what to PDC

A

Activates posphatase, actives PDC

60
Q

Which enzymes make NADH

A

Malate dehydrogenase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase

61
Q

Which enzymes release CO2

A

a-ketoglutarate dehydrogenase, isocitrate dehydrogenase

62
Q

Which enzymes make FADH

A

Succinate dehydrogenase

63
Q

Which part of TCA makes GTP

A

Succinyl CoA to succinate

64
Q

Pyruvate dehydrogenase complex

A

CO2 leaves from a-keto acid
a-keto acid decarboxylase transfers the acyl from the keto acid to TPP

65
Q

E1 cofactors

A

(pyruvate dehydrogenase)
TPP

66
Q

E2 cofactors

A

(Lipoate containing transacyclase)
Lipoate
CoA

67
Q

E3 coafactors

A

(dihydrolipoyl dehydrogenase)
CoA
FAD

68
Q

What is malate dehydrogenase inhibited by

A

NADH

69
Q

What is isocitrate dehydrogenase and a-ketoglutarate are activated

A

Ca2+

70
Q

What is isocitrate dehydrogenase and a-ketoglutarate are inhibited by

A

NADH

71
Q

What is a-ketoglutarate dehydrogenase inhibited by

A

NADH

72
Q

What is a-ketoglutarate dehydrogenase activated by

A

Ca2+

73
Q

Which step of PDC participates in all a-ketoacid dehydrogenase complexes?

A

E3

74
Q

Which step of PDC only participates in pyruvates?

A

E1 and E2

75
Q

What happens when NADH is too high

A

It inhibits the cycle and slows it down

76
Q

FA generates acetyl coA via

A

b-oxidation

77
Q

Which two processes are NOT energetically favorable

A

Malate to OAA
Citrate to isocitrate

78
Q

Which processes are energetically favorable

A

OAA to citrate
Isocitrate to a-ketoglutarate
a-ketoglutarate to succinyl CoA
Succinyl to succinate

79
Q

Which processes is the MOST energetically favorable

A

a-ketoglutarate to succinyl CoA

80
Q

What coenzymes does Pyruvate dehydrogenase complex require

A

NAD+, FAD, lipoic acid, TPP, COA
(B1, B2, B3, B5, lipoic acid)

81
Q

When are anaplerotic pathways used

A

During gluconeogenesis

82
Q

Sources of acetyl CoA

A

Palmitate, acetoacetate, glucose, pyruvate, alanine, ethanol

83
Q

PDC kinase is inhibited by

A

ADP
Pyruvate

84
Q

PDC kinase is activated by

A

Acetyl coa, NADH

85
Q

PDC is activated by

A

pyruvate, NAD+

86
Q

PDC is inactivated by

A

Acetyl coa, NADH

87
Q
A
88
Q
A

Biochemistry (13 decks)

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