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Biochem > Exam 2 M6 > Flashcards

Exam 2 M6 Flashcards

1
Q

T/F: biological rxns require catalysts

A

T

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2
Q

what serves as enzymes

A

proteins and RNA molecules

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3
Q

T/F: catalysts are not enzymes

A

F

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4
Q

enzymes catalyze rns under ____ conditions

A

mild

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5
Q

enzymes allow for high degrees of rxn ____

A

specificty

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6
Q

enzymes catalyze 1 or a few ___

A

closely related rxns

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7
Q

T/F: enzymes can’t distinguish btwn stereoisomers

A

False

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8
Q

T/F: enzymes inc rxn rates

A

T

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9
Q

how much do enzymes inc rxn rates

A

10^6 to 10^12

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10
Q

enzymes enable ___

A

regulation

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11
Q

how to regulate enzyme

A

1)control amount of enzyme in cell via txn (control rate at which RNA is produced that will code for that enzyme) or tsln (control how fast RNA–> protein) mechs

2)control activity of enzyme (different small molecules can act as effector molecules that can speed up an enzyme or slow down an enzyme –> activators vs inhibitors)

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12
Q

some enzymes require additional molecules called ____ for their functions

A

coenzymes

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13
Q

Cofactors

A
  1. Cations (ions that stabilize enzyme structure like Zn fingers; can also participate directly in chemical rxns)
  2. coenzymes (organic molecules that associate transiently w enzyme; can also participate in chemical rxn and need to be converted back to their initial state for next round of rxn)
  3. prosthetic groups (e.g. heme, organic molecules permanently covalently associated w enzyme)
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14
Q

active sites are meant to be complementary in ____ to substrate

A

shape and chemical properties

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15
Q

enzymes are HIGHLY

A

specific

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16
Q

enzymes are not ____

A

rigid

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17
Q

enzymes do not alter ____

A

thermodynamics

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18
Q

define transition state

A

point of highest free energy

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19
Q

rate of rxn is directly proportional to

A

delta G dagger

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20
Q

enzymes don’t affect the ____ of equilibrium

A

position

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21
Q

T/F: If a rxn is +deltaG but an enzyme can catalyze it, it will occur

A

F

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22
Q

how do enzymes speed up rxns

A

by stabilizing TS by reducing deltaG associated w TS, make substrates that resemble TS, or change the pathway to go through a diff TS

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23
Q

what causes high delta G

A

lots of breaking and forming bonds at the same time

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24
Q

what is delta delta G dagger

A

reduction in deltaG dagger by the catalyst; helps determine how much enzyme speeds up rxn

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25
Q

enyme does not change overall ___ of a rxn

A

deltaG

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26
Q

enzymes do change ____ of a rxn by lowering delta G associated w TS

A

kinetics

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27
Q

all chem rxns exhibit___

A

kinetics

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28
Q

zero order

A

rate = k1
A–> B
k1
independent of concentration and only depends on rate constant, k1

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29
Q

first order

A

rate = k1[A]
A–> B
k1
depends on rate constant and also on conc of reactants

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30
Q

second order

A

rate = k1[A][B]
A+B –> C
k2
depends on rate constant and conc of reactants

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31
Q

dissociation constant for ES

A

Kd = [E][S]/[ES]

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32
Q

what does Kd for ES assume

A

K-1&raquo_space; K2

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33
Q

which molecules can’t you measure in lab

A

[E], [ES]

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34
Q

which molecules can you measure in lab

A

[P], [E]tot

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35
Q

what enzyme did M-M base their model off of

A

invertase

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36
Q

what are the 3 assumptions of M-M’s model

A
  1. product does not convert back into substrate (irreversible rxn)
  2. rxn is at a steady-state; [ES] remains constant during whole rxn
  3. [S] is infinitely large
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37
Q

product formation depends on _____ and ___

A

[ES] and K2

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38
Q

M-M equation

A

v0 = vmax [ S] / (Km + [S])

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39
Q

a low [S], line is almost linear but as we inc [S], v inc in a ___ fashion

A

linear

40
Q

Km = [S] it takes to get to

A

1/2 Vmax

41
Q

vmax occurs

A

at high [S] when enzyme is sat
vmax = k2 [E]tot

42
Q

Kcat =

A

Vmax / [E]tot

43
Q

Kcat also known as

A

turnover number

44
Q

large Kcat =

A

fast conversion and high turnover #

45
Q

for enzymes that obey M-M kinetics, Kcat =

A

K2

46
Q

highly efficient enzymes are ___ limited

A

diffusion

47
Q

overall efficiency of an enzyme depends on both ___ and ____

A

Kcat and Km

48
Q

Kcat/Km must be less than or equal to

A

K1

49
Q

efficiency is directly proportional to

A

Kcat

50
Q

efficiency is indireclty proportional to

A

Km

51
Q

on LW-B plot: slope =

A

Km/Vmax

52
Q

on LW-B plot: x-intercept =

A

-1/Km

53
Q

on LW-B plot: y-intercept =

A

1/Vmax

54
Q

competitive inhibition blocks the

A

active site (direclty or allosterically)
block’s enzyme’s ability to bind substrate

55
Q

T/F: comp inhibition binds enzymes reversibly or irreversibly

A

T

56
Q

comp inhibitors often resemble

A

substrate in structure

57
Q

comp inhibitors best resemble

A

TS analog

58
Q

product inhibition is an ex of ____ inhibition

A

competitive

59
Q

inhibitors change the ___

A

kinetics

60
Q

comp inhibitors bind to

A

free enzyme

61
Q

KI =

A

[E][I]/[EI]

62
Q

M-M equation for comp inhibition

A

V0 = Vmax [ S] / aKm + [S]

63
Q

For comp inhbition, as inc [I], the line shifts to the ___ which means rxn is slower

A

right

64
Q
A
65
Q
A
66
Q
A
67
Q
A
68
Q

alpha depends on

A

[I] and affinity of E for I

69
Q

Km app =

A

alpha Km

70
Q

for comp inhibition, alpha only affects

A

Km

71
Q

slope for comp inhib

A

alpha Km / Vmax

72
Q

in comp inhib, Vmax

A

doesnt change

73
Q

if inhibitor binds very tightly, KI ___ and alpha ___

A

dec; inc

74
Q

uncomp inhibitors bind to

A

ES complex

75
Q

uncomp inhibitors interfere with

A

catalysis

76
Q

uncomp inhibitors don’t necessarily need to resemble

A

substrate bc doesn’t bind to active site

77
Q

KI’ =

A

[ES][I]/[ESI]

78
Q

uncomp inhib graph looks like

A

parallel lines

79
Q

why are the parallel lines parallel

A

bc Vmax and Km are changing proportionally as we inc [I]

80
Q

a’ is_____ to [I]

A

directly proportional

81
Q

a’ is _____ to KI

A

indireclty proprtional

82
Q

uncomp inhibitor effects both ___

A

Vmax and Km

83
Q

as we add more uncomp inhibitor, Km___and Vmax __

A

inc; dec

84
Q

new y-int for uncomp inhib

A

a’/vmax

85
Q

new x-int for uncomp inhib

A

-a’/Km

86
Q

M-M equation for uncomp inhib

A

V0 =(vmax/a’)[S] / (Km/a’) +[S]

87
Q

Km app for uncomp inhib

A

Km / a’

88
Q

vmax app for uncomp inhib

A

vmax / a’

89
Q

both vmax and Km is affected by

A

a’

90
Q

mixed inhib affects both

A

binding (comp) and catalysis (uncomp)

91
Q

M-M equation for mixed

A

V0 = (vmax/a’)[S] / (aKm/a’) + [S]

92
Q

Km app for mixed =

A

aKm/a’

93
Q

Vmax app for mixed

A

Vmax/a’

94
Q

in mixed, both a and a’ affects

A

Km

95
Q
A

Biochem (6 decks)

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