19. CAC cycle

Question 1

how many steps are there in the CAC

Answer 1

8

Question 2

how many of the 8 steps of the CAC are oxidations

Answer 2

4

Question 3

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

Answer 3

reduced electron carriers: NADH or FADH2

Question 4

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

Answer 4

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

Question 5

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

Answer 5

citrate (6C)

claisen condensation

Question 6

step 1: what enzyme is used

Answer 6

citrate synthase

Question 7

step 1: what happens to the free CoA

Answer 7

it can return to the PDH complex

Question 8

step 1: describe the delta G’o

Answer 8

large and negative

Question 9

step 1: describe how acetyl CoA and OAA are joined

Answer 9

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

Question 10

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

Answer 10

H2O converting to CoA-SH

Question 11

step 1: describe the structure of citrate synthase

Answer 11

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

Question 12

step 1: reversible or irreversible

Answer 12

irreversible

Question 13

step 2: what is the reagent and product

Answer 13

citrate into isocitrate

Question 14

step 2: reversible or irreversible

Answer 14

reversible

Question 15

step 2: what is the intermediate produced

Answer 15

cis-aconitate

Question 16

step 2: what enzyme is used

Answer 16

aconitase

Question 17

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

Answer 17

true

Question 18

step 2: what type of reaction is this

Answer 18

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

Question 19

step 3: what is the reagent and product

Answer 19

isocitrate into a-ketoglutarate

Question 20

step 3a: what does isocitrate first convert to

Answer 20

oxalosuccinate

Question 21

step 3a: what enzyme converts isocitrate to oxalosuccinate

Answer 21

isocitrate dehydrogenase

Question 22

step 3a: what goes over the arrow

Answer 22

NAD(P)+ –> NAD(P)H + H+

Question 23

step 3a: what kind of reaction is this

Answer 23

oxidation

Question 24

step 3b: what does oxalosuccinate convert to

Answer 24

an intermediate

Question 25

step 3b: what goes over the arrow

Answer 25

loss of CO2

Question 26

step 3b: what type of reaction is this

Answer 26

decarboxylation

Question 27

step 3c: what does the intermediate convert to

Answer 27

a-ketoglutarate

Question 28

step 3c: what type of reaction is this

Answer 28

rearrangement

Question 29

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

Answer 29

oxidative decarboxylation (via loss of CO2)

Question 30

step 3: overall, what happens to electron carriers

Answer 30

carriers get reduced by the electrons from the oxidation

Question 31

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

Answer 31

glutamate

Question 32

step 4: reagent and product?

Answer 32

a-ketoglutarate into succinyl-CoA

Question 33

step 4: what type of reaction is this

Answer 33

oxidative decarboxylation

Question 34

step 4: what enzyme is used

Answer 34

a-ketoglutarate dehydrogenase complex

Question 35

step 4: what goes over the arrows

Answer 35

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

Question 36

step 4: what happens to the electron carriers

Answer 36

NAD+ converts to the reduced NADH

Question 37

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

Answer 37

the product becomes activated

Question 38

step 4: describe the delta G'o

Answer 38

large and negative

Question 39

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

Answer 39

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

Question 40

step 5: reagent and product?

Answer 40

succinyl-CoA to succinate

Question 41

step 5: enzyme used?

Answer 41

succinyl-CoA synthetase

Question 42

step 5: what type of reaction is this

Answer 42

oxidative decarboxylation/substrate level phosphorylation

Question 43

step 5: what goes over the arrow

Answer 43

GDP into GTP and CoA-SH

Question 44

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

Answer 44

true

Question 45

step 6: reagent and product?

Answer 45

succinate to fumarate

Question 46

step 6: enzyme used

Answer 46

succinate dehydrogenase

Question 47

step 6: what type of reaction is this

Answer 47

oxidation/dehydrogenation

Question 48

step 6: what happens to electron carriers

Answer 48

FAD reduced to FADH2

Question 49

step 6: describe the location and structure of succinate dehydrogenase

Answer 49

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

Question 50

step 7: reagent and product?

Answer 50

fumarate to L-malate

Question 51

step 7: enzyme used?

Answer 51

fumarase

Question 52

step 7: type of reaction?

Answer 52

hydration (addition of water)

Question 53

step 8: reagent and product?

Answer 53

L-malate to OAA

Question 54

step 8: enzyme used?

Answer 54

L-malate dehydrogenase

Question 55

step 8: what happens to electron carriers

Answer 55

NAD+ to reduced NADH

Question 56

step 8: what type of reaction?

Answer 56

dehydrogenation/oxidation

Question 57

how many carbons left as CO2

Answer 57

2

Question 58

how many NADH were made

Answer 58

3

Question 59

how many FADH2 were made

Answer 59

1

Question 60

how many ATP/GTP were made

Answer 60

1

Question 61

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

Answer 61

anaplerotic reactions

Question 62

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

Answer 62

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

Question 63

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

Answer 63

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

Question 64

what inhibits the PDH complex

Answer 64

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

Question 65

what activates the PDH complex

Answer 65

AMP, COA, and NAD+

Question 66

which steps is the CAC regulated at

Answer 66

1, 3, 4 (all highly exergonic)

Question 67

what inhibits the CAC

Answer 67

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