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glycogen > Synthesis of Acetyl Coa > Flashcards

Synthesis of Acetyl Coa Flashcards

1
Q

what kind of enzyme would make sense for the conversion of pyruvate to aetyl coa

A

it would make sense to use a decarboxylase because we just pop off a co2!

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2
Q

what is a multi enzyme complex

A

they are huge proteins that have multiple reaction centers . think of them as a mall!

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3
Q

what are some advantages of multienzyme complexes

A

everything is one reaction center, channels, everything is kept “in house”

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4
Q

what is the name of the multienzyme complex that forms Acetyl-CoA ?

A

Acetyl-CoA is formed from pyruvate through oxidative decarboxylation by a multienzyme complex named pyruvate dehydrogenase.

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5
Q

what 3 enzymes are located on the pyruvate dehydrogenase complex?

A

This complex contains multiple copies of three enzymes: pyruvate dehydrogenase (E1), dihydrolipoyl transacetylase (E2), and dihydrolipoyl dehydrogenase (E3).

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6
Q

thiamine pyrophosphate (cofactor )has what function? and where is it bound ?

A

it decarboxylates pyruvate . It is bound to E1

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7
Q

Lipoic acid (cofactor)has what function? and where is it bound ?

A

accepts carbanion from tpp. E2

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8
Q

Coa

A

in E2 accepts acytyl group

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9
Q

flavin adenine

A

E3, reduced by lipoamide

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10
Q

Nad

A

E3 reduced by FADH2

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11
Q

Pyruvate dehydrogenase requires which cofactor ?

A

Pyruvate dehydrogenase (E1), a TPP-requiring enzyme, decarboxylates pyruvate with the formation of a hydroxyethyl-TPP intermediate

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12
Q

dihydrolipoyl transacetylase (E2), which contains which cofactor

A

dihydrolipoyl transacetylase (E2), which contains a lipoamide group.

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13
Q

Draw the 5 reactions of the pyruvate dehydrogenase multi enzyme

A

slide 17-6

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14
Q

what is the entire multienzyme complex called

A

pyruvate dehydrogenase

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15
Q

what is the first enzyme of the pyruvate dehyrogenase complex called

A

it is called pyruvate dehydrogenase (like ny ny). This is E1.

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16
Q

the dihydrolipoyl transacetace complex does what to the pyruvate dehyrogenase complex and what part of the enzyme is this

A

this reaction transfers the actyl group . this is E2

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17
Q

what is E3 called

A

dihydrolipoyl dehydrogenase

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18
Q

what is the last step of the multienzyme complex

A

reducing NAD and oxidizing dihydrolipoyl dehydrogenase

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19
Q

is FAD a cosubstrate or a prosthetic group

A

prosthetic group

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20
Q

KNOW HOW TO DRAW MULTI ENZYME COMPLEX

A

ON TEST

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21
Q

when pyruvate has been transferred into the mitochondrial matrix what cycle is starting

A

citric acid cycle

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22
Q

where does the citrix acid cycle take place

A

in the mitochondrial matrix

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23
Q

what effect does arsenic have on the dihydrolipoamide?

A

it does something to the dihydrolipoamide

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24
Q

which complex does arsenic mess up

A

e2, it would shut off acytyl coa

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25
Q

is citrate synthase a reversible reaction?

A

no!!! its about -30kj . this is the importance of starting at acytl coa

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26
Q

is isocitrate chiral ?

A

yes

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27
Q

why is succinyl coa synthesate reversible?

A

becaue it chops off a coa which gives some negative delta g

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28
Q

do we double the citric acid cycle if we are coming from glycolyis?

A

yes

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29
Q

in which parts of the citric acid cycle do nadh come out

A

0, 3,4,8

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30
Q

in which step does FADH2 come out

A

6

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31
Q

why is the transition from acytly to citrate only one direction?

A

because the coa comes off which means it has a delta g of negative 30

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32
Q

pyruvate dehydrogenase and alpha ketoglutarate dehydrogenase have multienzyme complec so can get arsnic poisoining

A

fyi! must know this

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33
Q

what kind of linkage attaches a coA

A

sulfhydrol

34
Q

what does substrate level phosphorylation

A

way to make atp or nucleotide wihtout the need for 02.

35
Q

substrate level phosporylation is also make by pk and pgk

A

these are the steps

that make atp without o2.

36
Q

is there substrate level phosphorylation in gluconeogeneis?

A

look up

37
Q

if someone has hypophosphetemia what step of the citric acid cycle would they have trouble with

A

step 5 because they have no phosphates in the mitochondria, because they do not have the apporpiate transporters.

38
Q

talk about the idea of coupling going from malate to oxaloacetate

A

the citrate synthase avery strong negative delta with powers this reaction.

39
Q

what must you come in the citric acid as in order to complete the loop

A

acytyl coa. this is because the enzyme citrate synthase will be bypassed

40
Q

if we throw in anything into the citric acid that is below acytly coa where will cycle stop

A

malate

41
Q

if we use malic enzyme what is reduced and oxidized and what is released

A

co2 comes out . nadph is getting reduced

42
Q

is it hard or easy to concentrate oxaloacetate

A

it is hard, because it is fleeting due to the negative delta g

43
Q

what does malic enzyme do

A

it will convert malate to pyruvate .

44
Q

wher does malic enzyme function

A

in the cytosol.

45
Q

if you put in 4 carbons how many co2 will come out

A

4

46
Q

if you putin 5 carbon howmany 5 co2 will come out

A

5

47
Q

what is the delta g of citrate synthase

A

it is about - 30 kj

48
Q

which enzymes have the multienzyme complexes

A

1 and 4

49
Q

what would E1 be called on alpha keto glutarate

A

alpha keto glutarate dehydrogenase

50
Q

what would E2 be called on alpha ketoglutarate

A

dihydrobutyl (4 carbons) transsucinnylase

51
Q

what does e3 do

A

its an oxidation agent.

52
Q

what would E3 be called on alpha ketoglutarate

A

dihydroliply dehydrogenase

53
Q

if FADH makes atp where is it located

A

on the mitochondrial membrane

54
Q

t/f we can control citric acid cycle with allosteric and covalent modification

A

true

55
Q

if we have too much acytyl coa and NADH what will happen?

A

it will be an inhibitor. it is an example of product inhibition . E2 and E3 are points of control

56
Q

Why is the first step of citric acid cycle a good point of regulation

A

The decarboxylation of pyruvate by the pyruvate dehydrogenase complex is irreversible, and since there are no other pathways in mammals for the synthesis of acetyl-CoA from pyruvate, it is crucial that the reaction be precisely controlled. Two regulatory systems are used:

57
Q

Product inhibition by NADH and acetyl-CoA

A

how does this work?

58
Q

is the

A

active when its dephophorylate

59
Q

what is one advantage of removing co2

A

it gives us some energy through a negative delta g

60
Q

under what condtions is malate dehydrogenase reversible ?

A

when citrate synthase has started the cycle( acytyl coa is invovled)

61
Q

what is a molecule that we can use to regulate the citric acid cycle that is under allosteric control

A

acytyl co A, if we dont have it we cant even start the cycle . NADH can also be used as a form of allosteric control

62
Q

What parts of the pathway are citrate and NADH involved in regulation

A

in E2 and E3 because they just left the active site . They drive the reversible transacetylase (E2) and dihydrolipoyl dehydrogenase (E3) reactions backward.

63
Q

what are forms of covalent modification in which we can control regulation of the citric acid cycle?

A

Covalent modification by phosphorylation/dephosphorylation of E1

64
Q

Explain how

A

In eukaryotes, the products of the pyruvate dehydrogenase reaction, NADH and acetyl-CoA, also activate the pyruvate dehydrogenase kinase associated with the enzyme complex.
The resulting phosphorylation of a specific dehydrogenase Ser residue inactivates the pyruvate dehydrogenase complex.

65
Q

glycogen synthase is synonomous with pyruvate dehydrogenase

A

So if it is dephos its turned on and phos its turned off

66
Q

T/F insulin activates pyruvate dehydrogenase

A

true

67
Q

The regulatory enzymes of the citric acid cycle seem to control flux primarily by three simple mechanisms:

A

Substrate availability
Product inhibition
Competitive feedback inhibition by intermediates further along the cycle.

68
Q

In terms of substrate availiability . What are types of substrate that we can use to choke off citric acid cycle?

A

removing :NAD+, Acytyl Coa, GTP, FAD, coA

69
Q

If we inhibit transport into the matrix will the citric acid cycle work

A

no ! since we are in the matrix all of the reactants must be in through transporters

70
Q

what are some examples of product inhibition

A

NADH, FADH, GTP, COA

71
Q

what are the 3 enzymes in the citric acid cycle that are stimulated by calcium

A

pyruvate dehydrogenase , isocitrate dehydrogenase , alpha keto glutorate dehydrogenase

72
Q

what is a kelator

A

it is like a sponge for a particular iion.

73
Q

what effect would a calcium keylator have on the citric acid cycle

A

it would increase the production of oxaloacetate in the citric acid cycle

74
Q

what effect would ADP have on the citric acid cycle

A

it would enhance the citric acid cycle

75
Q

list to activators of citric acid cycle and what steps do they affect

A

Ca, ADP . Step 1 ,3,4

76
Q

what are some inhibitors of the citric acid cycle

A

NADH

77
Q

what steps of the citric acid cycle does NADH inhibit

A

pyruvate dehydrogenase (1), citrate synthase, alpha ketoglutarate dehydrogenase,

78
Q

citrate goes back to glycolysis at pfk

A

on test

79
Q

t/f insulin turns on citric acid cycle in a well fed state by activating pyruvate dyhydrogenase

A

yes, it does, it seems weird but it bottle necks everything at citrate and it gets ejected out of the mitochondria into the cytosol for storage.

80
Q

where is pyruvate dehydrogenase found

A

in the mitochondria

glycogen (4 decks)

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