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BIOL 2421 - Cellular Biochem > 19. CAC cycle > Flashcards

19. CAC cycle Flashcards

1
Q

how many steps are there in the CAC

A

8

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2
Q

how many of the 8 steps of the CAC are oxidations

A

4

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3
Q

what form is the energy in that is released from the CAC

A

reduced electron carriers: NADH or FADH2

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4
Q

step 1: what are the reagents and how many carbons are they

A

acetyl-CoA (2C) and OAA (4C)

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5
Q

step 1: what do acetyl CoA and OAA join to produce + what type of reaction is this

A

citrate (6C)

claisen condensation

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6
Q

step 1: what enzyme is used

A

citrate synthase

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7
Q

step 1: what happens to the free CoA

A

it can return to the PDH complex

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8
Q

step 1: describe the delta G’o

A

large and negative

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9
Q

step 1: describe how acetyl CoA and OAA are joined

A

the methyl of acetyl CoA is joined to the carbonyl carbon of OAA

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10
Q

step 1: other than the enzyme, what is over the arrow

A

H2O converting to CoA-SH

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11
Q

step 1: describe the structure of citrate synthase

A

homodimer, one domain is flexible in each subunit and undergoes a conf. change upon OAA binding. This exposes the binding site for acetyl CoA

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12
Q

step 1: reversible or irreversible

A

irreversible

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13
Q

step 2: what is the reagent and product

A

citrate into isocitrate

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14
Q

step 2: reversible or irreversible

A

reversible

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15
Q

step 2: what is the intermediate produced

A

cis-aconitate

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16
Q

step 2: what enzyme is used

A

aconitase

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17
Q

step 2: T or F; the enzyme aconitase is used for both halves of the reaction

A

true

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18
Q

step 2: what type of reaction is this

A

dehydration, then rehydration. The OH group of citrate gets repositioned to isocitrate

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19
Q

step 3: what is the reagent and product

A

isocitrate into a-ketoglutarate

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20
Q

step 3a: what does isocitrate first convert to

A

oxalosuccinate

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21
Q

step 3a: what enzyme converts isocitrate to oxalosuccinate

A

isocitrate dehydrogenase

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22
Q

step 3a: what goes over the arrow

A

NAD(P)+ –> NAD(P)H + H+

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23
Q

step 3a: what kind of reaction is this

A

oxidation

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24
Q

step 3b: what does oxalosuccinate convert to

A

an intermediate

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25
Q

step 3b: what goes over the arrow

A

loss of CO2

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26
Q

step 3b: what type of reaction is this

A

decarboxylation

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27
Q

step 3c: what does the intermediate convert to

A

a-ketoglutarate

28
Q

step 3c: what type of reaction is this

A

rearrangement

29
Q

step 3: overall, what type of reaction is the conversion of isocitrate to a-ketoglutarate

A

oxidative decarboxylation (via loss of CO2)

30
Q

step 3: overall, what happens to electron carriers

A

carriers get reduced by the electrons from the oxidation

31
Q

step 3: what amino acid is a-ketoglutarate the a-keto acid of

A

glutamate

32
Q

step 4: reagent and product?

A

a-ketoglutarate into succinyl-CoA

33
Q

step 4: what type of reaction is this

A

oxidative decarboxylation

34
Q

step 4: what enzyme is used

A

a-ketoglutarate dehydrogenase complex

35
Q

step 4: what goes over the arrows

A

CoA-SH and NAD+ go in, NADH and CO2 come out

36
Q

step 4: what happens to the electron carriers

A

NAD+ converts to the reduced NADH

37
Q

step 4: what is the purpose of adding CoA to the product

A

the product becomes activated

38
Q

step 4: describe the delta G’o

A

large and negative

39
Q

step 4: what are the implications of the large negative delta G’o

A

the release of the energy upon succinyl-CoA hydrolysis is used to synthesize ATP or GTP in step 5

40
Q

step 5: reagent and product?

A

succinyl-CoA to succinate

41
Q

step 5: enzyme used?

A

succinyl-CoA synthetase

42
Q

step 5: what type of reaction is this

A

oxidative decarboxylation/substrate level phosphorylation

43
Q

step 5: what goes over the arrow

A

GDP into GTP and CoA-SH

44
Q

step 5: T or F: the GTP produced can also be considered to be ATP

A

true

45
Q

step 6: reagent and product?

A

succinate to fumarate

46
Q

step 6: enzyme used

A

succinate dehydrogenase

47
Q

step 6: what type of reaction is this

A

oxidation/dehydrogenation

48
Q

step 6: what happens to electron carriers

A

FAD reduced to FADH2

49
Q

step 6: describe the location and structure of succinate dehydrogenase

A

membrane bound (IMM), and active site faces the matrix (plays a role in the ETC)

50
Q

step 7: reagent and product?

A

fumarate to L-malate

51
Q

step 7: enzyme used?

A

fumarase

52
Q

step 7: type of reaction?

A

hydration (addition of water)

53
Q

step 8: reagent and product?

A

L-malate to OAA

54
Q

step 8: enzyme used?

A

L-malate dehydrogenase

55
Q

step 8: what happens to electron carriers

A

NAD+ to reduced NADH

56
Q

step 8: what type of reaction?

A

dehydrogenation/oxidation

57
Q

how many carbons left as CO2

A

2

58
Q

how many NADH were made

A

3

59
Q

how many FADH2 were made

A

1

60
Q

how many ATP/GTP were made

A

1

61
Q

what is the name for the type of reactions that replenish either OAA or malate

A

anaplerotic reactions

62
Q

describe how the flow of C into the CAC is controlled at the transport of pyruvate into the mitochondria

A

pyruvate can easily pass through large pores in the OMM, and then the mitochondrial pyruvate carrier on the IMM allows it to pass into the matrix

63
Q

describe how the flow of C into the CAC is controlled at the conversion of pyruvate to acetyl-CoA

A

PDG complex is inhibited by reversible phosphorylation on an E1 serine. PDH includes a kinase and a phosphoprotein phosphatase to complete the regulation, and the kinase is activated by ATP

64
Q

what inhibits the PDH complex

A

ATP, acetyl CoA, and NADH (downstream products catalyzed by PDH)

65
Q

what activates the PDH complex

A

AMP, COA, and NAD+

66
Q

which steps is the CAC regulated at

A

1, 3, 4 (all highly exergonic)

67
Q

what inhibits the CAC

A

high levels of the products (ATP and NADH) and also citrate (product of step 1)

BIOL 2421 - Cellular Biochem (21 decks)

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