6-enzymes B

Question 1

how can you measure the rate of a chemical reaction

Answer 1

the appearance of product or disappearance of substrate

Question 2

what remains constant under steady state condition

Answer 2

concentration of intermediate [ES]

Question 3

what is an example reaction in enzyme kinetics

Answer 3

E+S - ES - E+P

Question 4

what is k cat in relation to other K’s

Answer 4

the k constant from ES –> E + P

its the same as k2

Question 5

what is k2

Answer 5

the k constant from ES –> E + P

its the same as kcat

Question 6

what is k1

Answer 6

the k constant from E +S –> ES

Question 7

what is k-1

Answer 7

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

Question 8

what does total enzyme equal [E total]

Answer 8

[E] + [ES]

Question 9

what does the Michaelis constant reflect (Km)

Answer 9

the balance between formation and breakdown of the ES complex

Question 10

what happens to Vmax if you half the amount of enzymes

Answer 10

then its reduced by half too

Question 11

what does [S]= if Vo=0.5Vmax

Answer 11

then [S]=Km

Question 12

what is Vo when [S]=Km

Answer 12

1/2 Vmax

Question 13

what does a small Km mean (2 things)

Answer 13

better affinity, less substrate requirted to get to max velocity

Question 14

what does Kcat mean (2 words)

Answer 14

its the turnover number

Question 15

what does the kcat constant represent

Answer 15

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

Question 16

what do the lineweaver-Burk plots do

Answer 16

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

Question 17

which k value does Vmax reflect

Answer 17

Kcat

Question 18

what does specificity constant indicate

Answer 18

catalytic perfection

Question 19

what can indicate catalytic perfection

Answer 19

specificity constant

Question 20

what is the # range for catalytic perfection

Answer 20

10^8 - 10^9/Msc

Question 21

what does the specificity constant mean for an enzyme

Answer 21

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

Question 22

what unit is specificity constant in

Answer 22

M-1 s-1

Question 23

what do irreversible inhibitors do

Answer 23

covalently bind to enzymes

Question 24

what do reversible inhibitors do

Answer 24

non-covalently associate with enzymes

Question 25

what are 3 types of reversible inhibition

Answer 25

competitive uncompetitive mixed/non competitive

Question 26

what do irreversible enzymes do to rate of reaction

Answer 26

reduce

Question 27

what happens in competitive inhibition

Answer 27

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

Question 28

what does KI mean

Answer 28

dissociation constant

Question 29

what is KI (dissociation constant) for competitive inhibition

Answer 29

[E][I] / [EI]

Question 30

What does a competitive inhibitor do to apparent Km

Answer 30

increases

Question 31

what is another name for apparent Km

Answer 31

α Km

Question 32

what is another name for α Km

Answer 32

apparent Km

Question 33

what does the α factor reflect

Answer 33

the number of available active sites

Question 34

what does competitive inhibition do to apparent Vmax

Answer 34

doesnt change

Question 35

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

Answer 35

(αKm)/(Vmax)

Question 36

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

Answer 36

bigger α makes a less steep slope

Question 37

does Km affect slope

Answer 37

yes

Question 38

does Km affect intercept

Answer 38

no

Question 39

what is uncompetitive inhibition

Answer 39

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

Question 40

what is KI' for uncompetitive inhibition

Answer 40

[ES][I] / [ESI]

Question 41

where do uncompetitive inhibitors bind

Answer 41

to ES complex

Question 42

what is α'

Answer 42

a factor that reflects the number of effective active sites

Question 43

what happens to apparent Km with uncompetitive inhibition

Answer 43

it will decrease

Question 44

what happens to apparent Vmax in uncompetitive inhibition

Answer 44

it will decrease

Question 45

what does apparent Km= in uncompetitive inhibition

Answer 45

= Km/α'

Question 46

why would uncompetitive inhibitors decrease Km

Answer 46

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

Question 47

is Vmax or Km decreased more in uncompetitive inhibition

Answer 47

they are decreased by the same amounts

Question 48

what does Km represent (2 definitions)

Answer 48

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

Question 49

what does Km =

Answer 49

(K-1 + Kcat) / K1

Question 50

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

Answer 50

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

Question 51

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

Answer 51

Km/Vmax

Question 52

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

Answer 52

-α' / Km

Question 53

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

Answer 53

1/-αKm

Question 54

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

Answer 54

the slopes are the same

Question 55

where does a mixed inhibitor bind

Answer 55

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

Question 56

what is the K for mixed inhibition

Answer 56

both Ki and Ki' are in it

Question 57

what happens to apparent Vmax in mixed inhibition

Answer 57

it is decreased

Question 58

what happens to apparent Km in mixed inhibition

Answer 58

it will either increase or decrease

Question 59

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

Answer 59

Vmax is reduced and Km is unaffected

Question 60

what does apparent Km= in mixed inhibition

Answer 60

αKm / α'

Question 61

what does apparent Vmax= in mixed inhibition

Answer 61

Vmax / α'

Question 62

what do the relative slopes in mixed inhibition indicate

Answer 62

value of α

Question 63

what do the relative y intercepts in mixed inhibition indicate

Answer 63

value of α'

Question 64

what do the relative y intercepts in uncompetitive inhibition indicate

Answer 64

value of α'

Question 65

what do the relative slopes in competitive inhibition indicate

Answer 65

value of α

Question 66

what is apparent Vmax in competitive inhibition

Answer 66

keep same, Vmax

Question 67

what is apparent Vmax in noncompetitive inhibition

Answer 67

Vmax/α'

Question 68

what is apparent Vmax in uncompetitive inhibition

Answer 68

Vmax/α'

Question 69

what is apparent Vmax in mixed inhibition

Answer 69

Vmax/α'

Question 70

what is apparent Km in non competitive inhibition

Answer 70

same, Vmax

Question 71

what is apparent Km in competitive inhibition

Answer 71

αKm

Question 72

what is apparent Km in mixed inhibition

Answer 72

αKm/α'

Question 73

what is apparent Km in uncompetitive inhibition

Answer 73

Km/α'

Question 74

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

Answer 74

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

Question 75

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

Answer 75

α=α'

Question 76

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

Answer 76

α IS SMALLER THAN α'