midterm 2

Question 1

how to calculate Vmax

Answer 1

1/y int of lineweaver burke

Question 2

how to calculate km

Answer 2

-1/x int of lineweaver burke

Question 3

how to calculate Kcat

Answer 3

Vmax/[E]

Question 4

how is Vmax affected by change in [E]

Answer 4

affected proportionally; e.g. 1/2[E] ==> 1/2Vmax

Question 5

how is Km affected by change in [E]

Answer 5

it’s not

Question 6

how is Kcat affected by change in [E]

Answer 6

it’s not

Question 7

how to calculate efficiency of an enzyme

Answer 7

Kcat/Km

Question 8

where does a competitive inhibitor bind

Answer 8

the active site

Question 9

what changes occur during competitive inhibition (km, Vmax, etc)

Answer 9

Vmax does not change; Km increases

Question 10

where does an uncompetitive inhibitor bind and what does it affect

Answer 10

binds to ES complex without inhibiting substrate binding and inhibits catalytic function only

Question 11

what changes occur during uncompetitive inhibition (km, Vmax, etc)

Answer 11

decrease in Vmax, decrease in Km, no change in Km/Vmax (slopes are equal)

Question 12

relate Vmax (+I) to Vmax (-I) for uncompetitive inhibition

Answer 12

Vmax (+I) = Vmax (-I)/alpha’

Question 13

relate Km (+I) to Km (-I) for uncompetitive inhibition

Answer 13

Km (+I) = Km (-I)/alpha’

Question 14

where does a mixed inhibitor bind and what does it do

Answer 14

binds enzyme (at regulatory site) with or without substrate and inhibits both substrate binding and catalysis

Question 15

what changes occur during mixed inhibition (km, Vmax, etc)

Answer 15

decrease in Vmax, increase or decrease in Km

Question 16

where does a noncompetitive inhibitor bind and what does it do

Answer 16

binds enzyme equally with or without substrate and both inhibits substrate and catalysis

Question 17

what changes occur during mixed inhibition (km, Vmax, etc)

Answer 17

Vmax decreases, Km stays the same –> same percent inhibition overall; MM curve shifts down and left

Question 18

Relate Vmax (+I) to Vmax (-I) for a mixed inhibitor

Answer 18

Vmax(+I) = Vmax (-I)/alpha’

Question 19

relate Km (+I) to Km (-I) for a mixed inhibitor

Answer 19

Km (+I) = (alpha/alpha’)Km (-I)

Question 20

Relate Vmax (+I) to Vmax (-I) for a noncompetitive inhibitor

Answer 20

Vmax (+I) = Vmax (-I)/alpha’

Question 21

relate Km (+I) to Km (-I) for a noncompetitive inhibitor

Answer 21

Km (+I) = (alpha/alpha’)Km (-I) …. alpha = alpha’

Question 22

relate Km (+I) to Km (-I) for a competitive inhibitor

Answer 22

Km (+I) = alphaKm (-I)

Question 23

calculate alpha

Answer 23

alpha = 1 + [I]/Ki

Question 24

calculate alpha’

Answer 24

alpha’ = 1 + [I]/Ki’

Question 25

what does alpha relate to

Answer 25

free enzyme

Question 26

what does alpha’ relate to

Answer 26

E-S complex

Question 27

what does Ki and Ki’ tell you

Answer 27

affinity of enzyme to free enzyme and E-S complex, respectively

Question 28

2 methods to control velocity of enzyme catalyzed rxns

Answer 28

control of enzyme activity and control of amount of enzyme

Question 29

properties of an efficient enzyme

Answer 29

fast, catalyzing many reactions per second, and be able to accomplish this at a relatively low substrate concentration

Question 30

what is the michaelis menten equation (linearized and equal to Vo)

Answer 30

1/Vo = Km/(Vmax[S]) + 1/Vmax
Vo = (Vmax[S]) / (Km + [S])

Question 31

what are the 4 assumptions of michaelis menten

Answer 31

1. [S]&raquo_space;> [E}
2. catalysis is rate limiting: k2 «< k1
3. Vo = k2[ES]
4. [ES] at steady state: rate of formation = rate of breakdown

Question 32

what equation/chemical reaction is michaelis menten setup

Answer 32

E + S ES –> E + P

Question 33

energy charge regulation in anabolic pathways

Answer 33

ATP utilizing ==> activated by ATP, inhibited by ADP/AMP

Question 34

energy charge regulation in catabolic pathways

Answer 34

ATP regenerating ==> activated by AMP/ADP, inhibited by ATP

Question 35

What does a decrease in Km tell you about inhibitor affinity (E vs E-S)

Answer 35

higher binding affinity to E-S complex

Question 36

What does Ki > Ki’ tell you

Answer 36

the inhibitor has a stronger affinity for the E-S complex (dissociation constant for E-S is lower than for free enzyme)

Question 37

what does a Km increase tell you about inhibitor affinity (Ki)

Answer 37

increase in Km indicates a higher affinity for free enzyme

Question 38

how can an enzyme with a low kcat be efficient?

Answer 38

have a low Km, so it can bind substrate at relatively low concentrations