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BIOCH 320 > 6-enzymes B > Flashcards

6-enzymes B Flashcards

1
Q

how can you measure the rate of a chemical reaction

A

the appearance of product or disappearance of substrate

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2
Q

what remains constant under steady state condition

A

concentration of intermediate [ES]

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3
Q

what is an example reaction in enzyme kinetics

A

E+S - ES - E+P

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4
Q

what is k cat in relation to other K’s

A

the k constant from ES –> E + P

its the same as k2

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5
Q

what is k2

A

the k constant from ES –> E + P

its the same as kcat

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6
Q

what is k1

A

the k constant from E +S –> ES

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7
Q

what is k-1

A

the k constant from the reverse of E +S –> ES

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8
Q

what does total enzyme equal [E total]

A

[E] + [ES]

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9
Q

what does the Michaelis constant reflect (Km)

A

the balance between formation and breakdown of the ES complex

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10
Q

what happens to Vmax if you half the amount of enzymes

A

then its reduced by half too

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11
Q

what does [S]= if Vo=0.5Vmax

A

then [S]=Km

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12
Q

what is Vo when [S]=Km

A

1/2 Vmax

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13
Q

what does a small Km mean (2 things)

A

better affinity, less substrate requirted to get to max velocity

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14
Q

what does Kcat mean (2 words)

A

its the turnover number

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15
Q

what does the kcat constant represent

A

the ability of a single enzyme to catalyse product when it is saturated with substrate

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16
Q

what do the lineweaver-Burk plots do

A

generate a hyperbolic relationship between [S] and Vo - can be turned into a linear relationship

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17
Q

which k value does Vmax reflect

A

Kcat

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18
Q

what does specificity constant indicate

A

catalytic perfection

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19
Q

what can indicate catalytic perfection

A

specificity constant

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20
Q

what is the # range for catalytic perfection

A

10^8 - 10^9/Msc

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21
Q

what does the specificity constant mean for an enzyme

A

how good the enzyme is in respect to substrate, reflect specificity

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22
Q

what unit is specificity constant in

A

M-1 s-1

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23
Q

what do irreversible inhibitors do

A

covalently bind to enzymes

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24
Q

what do reversible inhibitors do

A

non-covalently associate with enzymes

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25
Q

what are 3 types of reversible inhibition

A

competitive
uncompetitive
mixed/non competitive

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26
Q

what do irreversible enzymes do to rate of reaction

A

reduce

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27
Q

what happens in competitive inhibition

A

the inhibitor resembles the substrate and competes with it for space in the active site

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28
Q

what does KI mean

A

dissociation constant

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29
Q

what is KI (dissociation constant) for competitive inhibition

A

[E][I] / [EI]

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30
Q

What does a competitive inhibitor do to apparent Km

A

increases

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31
Q

what is another name for apparent Km

A

α Km

32
Q

what is another name for α Km

A

apparent Km

33
Q

what does the α factor reflect

A

the number of available active sites

34
Q

what does competitive inhibition do to apparent Vmax

A

doesnt change

35
Q

what is the slope in competitive inhibition (with the 1/Vo vs 1/[S] graph)

A

(αKm)/(Vmax)

36
Q

what happens to competitive inhibition slope with increase α (in a normal Vo vs [S] graph)

A

bigger α makes a less steep slope

37
Q

does Km affect slope

A

yes

38
Q

does Km affect intercept

A

no

39
Q

what is uncompetitive inhibition

A

when the inhibitor binds to a site distinct from the substrate binding site AND only binds to an ES complex

40
Q

what is KI’ for uncompetitive inhibition

A

[ES][I] / [ESI]

41
Q

where do uncompetitive inhibitors bind

A

to ES complex

42
Q

what is α’

A

a factor that reflects the number of effective active sites

43
Q

what happens to apparent Km with uncompetitive inhibition

A

it will decrease

44
Q

what happens to apparent Vmax in uncompetitive inhibition

A

it will decrease

45
Q

what does apparent Km= in uncompetitive inhibition

A

= Km/α’

46
Q

why would uncompetitive inhibitors decrease Km

A

because they pull ES out of the equation, so the reaction shifts toward more ES formation where it will bind more substrate to the enzymes to create more ES, which leads to a lower Km

47
Q

is Vmax or Km decreased more in uncompetitive inhibition

A

they are decreased by the same amounts

48
Q

what does Km represent (2 definitions)

A

a relationship between various rate constants (michaelis constant)
the balance between formation and breakdown of the ES complex

49
Q

what does Km =

A

(K-1 + Kcat) / K1

50
Q

what are the effects of uncompetitive inhibitors at higher concentrations and why

A

a bigger effect because there is more ES complex to be attacked

51
Q

in the 1/Vo vs 1/[S] graph for uncompetitive inhibition, was is the value for slope

A

Km/Vmax

52
Q

in the 1/Vo vs 1/[S] graph for uncompetitive inhibition, was is the value for x intercept

A

-α’ / Km

53
Q

in the 1/Vo vs 1/[S] graph for competitive inhibition, was is the value for x intercept

A

1/-αKm

54
Q

how do the slopes compare in uncompetitive inhibition in e 1/Vo vs 1/[S] graph (with different α’ values)

A

the slopes are the same

55
Q

where does a mixed inhibitor bind

A

to a site distinct from the substrate binding site - either E alone or the ES complex

56
Q

what is the K for mixed inhibition

A

both Ki and Ki’ are in it

57
Q

what happens to apparent Vmax in mixed inhibition

A

it is decreased

58
Q

what happens to apparent Km in mixed inhibition

A

it will either increase or decrease

59
Q

what happens in mixed inhibition when α’=α (to Vmax and Km)

A

Vmax is reduced and Km is unaffected

60
Q

what does apparent Km= in mixed inhibition

A

αKm / α’

61
Q

what does apparent Vmax= in mixed inhibition

A

Vmax / α’

62
Q

what do the relative slopes in mixed inhibition indicate

A

value of α

63
Q

what do the relative y intercepts in mixed inhibition indicate

A

value of α’

64
Q

what do the relative y intercepts in uncompetitive inhibition indicate

A

value of α’

65
Q

what do the relative slopes in competitive inhibition indicate

A

value of α

66
Q

what is apparent Vmax in competitive inhibition

A

keep same, Vmax

67
Q

what is apparent Vmax in noncompetitive inhibition

A

Vmax/α’

68
Q

what is apparent Vmax in uncompetitive inhibition

A

Vmax/α’

69
Q

what is apparent Vmax in mixed inhibition

A

Vmax/α’

70
Q

what is apparent Km in non competitive inhibition

A

same, Vmax

71
Q

what is apparent Km in competitive inhibition

A

αKm

72
Q

what is apparent Km in mixed inhibition

A

αKm/α’

73
Q

what is apparent Km in uncompetitive inhibition

A

Km/α’

74
Q

in mixed inhibition, if the intercepts of the lines are above x axis, how are α and α’ related

why

A

α>α’

slope is increasing faster than Km, slope is affected by α and intercept is affected by α’

75
Q

in mixed inhibition, if the intercepts of the lines are at the x axis, how are α and α’ related

A

α=α’

76
Q

in mixed inhibition, if the intercepts of the lines are below the x axis, how are α and α’ related

why

A

α IS FUCKING SMALLER THAN α’

BIOCH 320 (16 decks)

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