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TCA Cycle & Oxidative Phosphorylation Flashcards

1
Q

Where does the link reaction take place?

A

Mitochondria

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2
Q

What is the link reaction?

A

Pyruvate + CoA + NAD+ –> acetyl CoA + carbon dioxide + NADH + H+

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3
Q

What kind of reaction is the link reaction?

A

Oxidative decarboxylation

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4
Q

What is the order of compounds in the TCA cycle?

A 
Oxaloacetate
| (+ acetyl CoA)
Citrate
|
Isocitrate
|
a-ketoglutarate
|
Succinyl CoA
|
Succinate
|
Fumarate
|
Malate
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5
Q

How many carbons does oxaloacetate have?

A

4

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6
Q

How many carbons does citrate have?

A

6

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7
Q

How many carbons does acetyl CoA have?

A

2

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8
Q

How many carbons does pyruvate have?

A

3

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9
Q

How many carbons does isocitrate have?

A

6

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10
Q

How many carbons does a-ketoglutarate have?

A

5

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11
Q

How many carbons does succinyl CoA have?

A

4

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12
Q

How many carbons does succinate have?

A

4

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13
Q

How many carbons does fumarate have?

A

4

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14
Q

How many carbons does malate have?

A

4

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15
Q

At which stages is carbon dioxide released in the TCA cycle?

A
  1. Isocitrate to a-ketoglutarate

4. a-ketoglutarate to succinyl CoA

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16
Q

What is the structure of oxalic acid?

A

HOOC–COOH

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17
Q

What is the structure of malonic acid?

A

HOOC–CH2–COOH

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18
Q

What is the structure of succinic acid?

A

HOOC–CH2–CH2–COOH

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19
Q

What is the structure of glutaric acid?

A

HOOC–CH2–CH2–CH2–COOH

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20
Q

What enzyme catalyses the formation of oxaloacetate to citrate?

A

Citrate synthase

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21
Q

What enzyme catalyses the formation of citrate to isocitrate?

A

Aconitase

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22
Q

What enzyme catalyses the formation of isocitrate to a-ketoglutarate?

A

Isocitrate dehydrogenase

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23
Q

What enzyme catalyses the formation of a-ketoglutarate to succinyl CoA?

A

a-ketoglutarate dehydrogenase

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24
Q

What enzyme catalyses the formation of succinyl CoA to succinate?

A

Succinyl CoA synthase/synthetase

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25
Q

What enzyme catalyses the formation of succinate to fumarate?

A

Succinate dehydrogenase

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26
Q

What enzyme catalyses the formation of fumarate to malate?

A

Fumarase

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27
Q

What enzyme catalyses the formation of malate to oxaloacetate?

A

Malate dehydrogenase

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28
Q

In which reactions is NAD+ reduced?

A
  1. Isocitrate to a-ketoglutarate
  2. a-ketoglutarate to succinyl CoA
  3. Malate to oxaloacetate
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29
Q

In what reaction is FAD reduced (TCA)?

A
  1. Succinate to fumarate
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30
Q

In what reaction is GTP produced (TCA)?

A
  1. Succinyl CoA to succinate
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31
Q

What is oxidative phosphorylation?

A

Reoxidation of NADH and FADH2 via the electron transport chain

Synthesis of ATP directly from ADP and Pi

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32
Q

How many reduced NAD+ are formed in one TCA cycle?

A

3

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33
Q

How many reduced FAD are formed in one TCA cycle?

34
Q

How many GTP are formed in one TCA cycle?

35
Q

How many ATP are formed per reoxidised NADH?

36
Q

How many ATP are formed per reoxidised FADH2?

37
Q

Which enzymes catalyse irreversible stages of the TCA cycle?

A
  1. Citrate synthase
  2. Isocitrate dehydrogenase
  3. a-ketoglutarate dehydrogenase
38
Q

What is another function of oxaloacetate?

A

Transamination to aspartate/aspartic acid

To form other amino acids, purines and pyrimidines

39
Q

What is another function of a-ketoglutarate?

A

Transamination to glutamate/glutamic acid

To form other amino acids and purines

40
Q

What is another function of succinyl CoA?

A

Used to form haem

41
Q

How is pyruvate converted back to glucose?

A

Pyruvate to oxaloacetate by pyruvate carboxylase

Oxaloacetate to phosphoenol pyruvate by PEP carboxylase

42
Q

What is another name for the electron transport chain?

A

Cytochrome chain

43
Q

Where is the electron transport chain found?

A

Embedded in inner mitochondrial membrane

44
Q

What components of the electron transport chain accept a pair of hydrogen atoms?

A

Flavin cofactors

Coenzyme Q

45
Q

What components of the electron transport chain accept an electron?

A

Iron-sulphur proteins

Cytochrome proteins

46
Q

Why can iron-sulphur proteins carry electrons?

A

Fe ion has variable oxidation states (Fe2+ Fe3+)

47
Q

Why can cytochrome proteins carry electrons?

A

Contain a haem ring with an Fe ion which has variable oxidation states

48
Q

What is an oxido-reduction (redox) potential?

A

Describes the ability of a carrier to donate its electron to another carrier

49
Q

In which direction do electrons flow between carriers?

A

More negative to more positive redox potentials

Highest to lowest energy carriers

50
Q

What is the highest energy electron carrier?

51
Q

What is the lowest energy electron carrier?

52
Q

What is the order of the components of the electron transport chain for NADH?

A

Complex I (NADH dehydrogenase complex)

CoQ (ubiquinone)

Complex III (cytochrome C reductase complex)

Cytochrome C

Complex IV (cytochrome C oxidase complex)

53
Q

What another name for complex I?

A

NADH dehydrogenase complex

54
Q

What is another name for complex III?

A

Cytochrome C reductase complex

55
Q

What is another name for complex IV?

A

Cytochrome C oxidase complex

56
Q

Where is CoQ found?

A

Embedded in inner mitochondrial membrane (long hydrophobic R group)

57
Q

What is another name for CoQ?

A

Ubiquinone

58
Q

Which components of the electron transport chain are mobile?

A

CoQ/ubiquinone

Cytochrome C

59
Q

What electron carriers are present in complex I?

A

Flavin mononucleotide

Iron-sulphur protein

60
Q

What electron carriers are present in complex III?

A

Cyt b

Iron-sulphur protein

Cyt c1

61
Q

What electron carriers are present in complex IV?

A

Cyt a

Cyt a3

62
Q

What happens at the complexes in the electron transport chain?

A

Electrons are passed step-wise between carriers

Energy released by transfer is used to actively pump protons from the mitochondrial matrix to the intermembrane space (not in complex II)

Oxygen reduced to water at complex IV

63
Q

What is the pH in the intermembrane space?

64
Q

What is the pH in the matrix?

65
Q

How is the pH gradient created across the inner mitochondrial membrane?

A

Active transport of protons out of the matrix by complexes in the electron transport chain

66
Q

What causes the voltage gradient across the inner mitochondrial membrane?

A

Charge difference/moving ions out of the matrix

67
Q

How do you calculate the electrochemical gradient across the inner mitochondrial membrane?

A

ΔV + ΔpH

68
Q

What is another term for electrochemical gradient?

A

Proton-motive force

69
Q

What energy transduction occurs when protons move through ATP-synthase?

A

Kinetic to mechanical (rotation/conformational change)

70
Q

Why is the electron transport chain for FADH2 different to that of NADH?

A

FADH2’s reducing ability/power is too weak to pass electrons to complex I so passes electrons to complex II instead

71
Q

What is the order of the components of the electron transport chain for FADH2?

A

Complex II

CoQ

Complex III (cytochrome C reductase complex)

Cytochrome C

Complex IV (cytochrome C oxidase complex)

72
Q

Which complex does not have the ability to move protons across the inner mitochondrial membrane?

A

Complex II

73
Q

Why is less ATP formed in the reoxidation of FADH2?

A

Complex II cannot pump protons across membrane

So smaller pH gradient

So smaller electrochemical gradient

So less protons moving through ATP-synthase

74
Q

What increases oxygen uptake for oxidative phosphorylation?

A

Increased ADP concentration

75
Q

What decreases oxygen uptake for oxidative phosphorylation?

A

Increased ATP concentration

76
Q

What can inhibit oxidative phosphorylation?

A

Carbon dioxide and carbon monoxide inhibit the cytochrome proteins by binding to haem group

Rotenone inhibits CoQ

77
Q

What does an uncoupler do?

A

Acts as a ‘back-door’ alternative to ATP-synthase for protons to move back into the matrix

78
Q

What is the effect of an uncoupler?

A

Energy from movement of protons across membrane not used to generate ATP but instead lost as heat

79
Q

Give an example of a good/beneficial uncoupler

A

Thermogenin protein in brown adipose tissue helps keep babies warm

80
Q

Give an example of a bad uncoupler

A

Dinitrophenol/DNP in weight loss pills

81
Q

How much ATP is generated from the complete oxidation of one glucose molecule?

A

30 or 32ATP

82
Q

Why can the amount of ATP generated by the complete oxidation of a glucose molecule vary?

A

NADH generated in glycolysis can be moved into mitochondria for oxidative phosphorylation by two different pathways

BMS07 (7 decks)

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