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Biochem > Exam 2 M7 > Flashcards

Exam 2 M7 Flashcards

1
Q

define allostery

A

how a molecule binding to one site on a protein can affect that protein’s activity at distal sites unrelated to where that molecule is binding to

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2
Q

how do cells control enzymatic activity

A

availability
physical env
substrate availability
allostery
physical/chemical changes
effectors

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3
Q

is there significant secondary structure change upon allosteric binding

A

no

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4
Q

T/F: allostery dec sensitivity of enzyme to substrate

A

F

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5
Q

inhibitors bind to and stabilize

A

T state

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6
Q

activators bind to and stabilize

A

R state

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7
Q

does M-M apply to allosteric enzymes

A

no

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8
Q

ATCase is involved in

A

first step of biosynthesis of pyrimidines

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9
Q

structure of ATCase

A

multisubunit; 6 catalytic and 6 regulatory

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10
Q

does ATCase have cooperative substrate binding

A

yes

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11
Q

allosteric inhibitor of ATCase

A

CTP

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12
Q

allosteric activator of ATCase

A

ATP

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13
Q

substrates of ATCase

A

carbamoyl phosphate and aspartate

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14
Q

substrates for ATCase are _____ charged

A

negatively

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15
Q

ATCase has a ____ velocity curve

A

sigmoidal

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16
Q

does ATCase obey M-M?

A

no

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17
Q

ATCase: catalytic trimers can be isolated and are active; ___ greater than holoenzyme

A

Vmax

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18
Q

ATCase: dimer of trimers plus trimer of dimers

A

(c3)2(r2)3

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19
Q

ATCase: allosteric regulators bind to ___ and substrate binds to ____

A

regulatory dimers; catalytic trimers

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20
Q

ATCase: catalytic trimers are high catalytically active and even ___ active than intact full enzyme w 12 subunits

A

more

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21
Q

ATCase: ____ slows down enzyme

A

regulatory subunits

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22
Q

ATCase: what happens when substrate binds

A

pushes catalytic trimers apart and separates them out and gives substrate more room to bind active site

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23
Q

ATCase: driving to R state

A

substrate binding to 1 monomer of catalytic subunit drives formation of R state in all single monomers; only need 1 monomer to be bound and then all other monomers are locked into R state w higher binding affinity

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24
Q

ATCase: In T state, steric hindrances prevent ___ binding domain from rotating into favorable position for substrate binding

A

Asp

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25
Q

ATCase: ___ binding drives structural changes that remove barrier to rotation

A

CP

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26
Q

ATCase: once CP binds, the two substrate binding domains reorient in each catalytic subunit to give___state with more accessible substrate binding sites

A

R

27
Q

ATCase: concerted ___ and ___ conf changes

A

tertiary; quaternary

28
Q

ATCase: T to R state transition requires ___

A

catalytic trimers to push away from each other, induced by substrate binding

29
Q

ATCase: each catalytic monomer has

A

2 domains

30
Q

ATCase: in R state, the 2 domains are

A

closer together/pinched together

31
Q

ATCase: 2 mvmts upon substrate binding that drives cooperativity

A

1)trimers push away from each other which gives more space for substrate to come in and bind
2)pinching in of domains so 2 substrates come in close proximity to each other so they can react

32
Q

ATCase has __ allosteric effectors

A

2

33
Q

ATCase: CTP binds to __ state where active sites are compressed

A

T

34
Q

ATCase: ATP binds to __ state where catalytic trimers are farther away from each other that allows substrate binding

A

R

35
Q

PFK: involved in

A

glycolysis

36
Q

substrates for PFK

A

F6P and ATP

37
Q

products of PFK

A

FBP, ADP

38
Q

inhibitor of PFK

A

ATP

39
Q

Activators of PFK

A

ADP, AMP

40
Q

PFK structure

A

tetramer

41
Q

PFK: for each subunit, there is a __ and ___

A

substrate binding site; allosteric regulatory site

42
Q

PFK: ATP is both __ and ___

A

substrate and allosteric inhibitor

43
Q

PFK: each subunit has ___ ATP binding sites

A

2; regualatory and substrate

44
Q

PFK: at substrate binding site, F6P binds to enzyme in __ state

A

R

45
Q

PFK: at substrate binding site, ATP binds to enzyme in ___ state

A

T or R

46
Q

PFK: at regulatory binding site, ATP binds enzyme in __ state

A

T

47
Q

PFK: at regulatory binding sites, AMP and ADP bind to __ state

A

R

48
Q

T/F: ATP levels are always constant

A

T

49
Q

PFK: ATP serves as a product ___

A

inhibitor

50
Q

PFK: R state helix is

A

full wound up and end has charged neg Glu

51
Q

PFK: R state Arg is in

A

substrate binding site

52
Q

PFK: Arg is in substrate binding site so that it

A

makes an ion pair w substrate and inc affinity btwn enzyme substrate in R state

53
Q

PFK: in T state, alpha helix is

A

not fully wound so neg Glu now in substrate binding site and Arg is over yonder and can’t form ionic interactions w substrate to inc stability

54
Q

PFK: In T state, neg Glu in substrate

A

repels neg charged F6P

55
Q

PFK: allosteric molecules bind to regulatory site causes ___

A

conf change that results in residue switch (+Arg in r state which favors interaction w F6P; -Glu in T state repels F6P)

56
Q

glycogen phosphorylase structure

A

dimer in 2 forms:
A = phosphorylated at Ser14
B = unphosphorylated

56
Q

PFK: need to be in __ state for catalysis to happen

A

R

57
Q

glycogen phosphorylase function

A

cleaves glycosidic bonds in glycogen

58
Q

glycogen phosphorylase: regulated by

A

allostery and phosphorylation (promotes R form)

59
Q

glycogen phosphorylase: phosphorylation of Ser14 transitions from __ to ___

A

T; R

60
Q

glycogen phosphorylase: what happens when N term gets phosphorylated

A

It swings out and tower helix tilts, moving green loop out of way of active site and Arg residues in active site reorient to bind substrate

61
Q

glycogen phosphorylase activator

A

AMP

62
Q

glycogen phosphorylase: AMP binds to __ state

A

R

63
Q
A

Biochem (6 decks)

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