Lecture 13: Kinetics

Question 1

how is zero order reactions interpreted when substrate independent?

Answer 1

unimolecular reaction

enzyme is saturated

Question 2

define Ka

Answer 2

association constant (make P)
Ka= [P]/ [S]

Question 3

Define Kd

Answer 3

dissociation constant (unmake P)
Kd= [S] / [P] = 1/ Ka

Question 4

Michaelis-Menten enzymes follow _______ order kinetics, but no matter what catalysis is not a _____ order reaction

Answer 4

first; first

Question 5

Define Km

Answer 5

Michaelis constant

[S] where reaction rate is half maximal OR half of the active sites are full

Question 6

Define Vmax

Answer 6

maximum velocity

maximum rate possible for a given concentration of enzyme

Question 7

Define Kcat

Answer 7

turnover number

number of substrate molecules converted per active site per time (first order rate constant)

Question 8

define Ks

Answer 8

a dissociation constant for substrate binding

Question 9

define Kcat/ Km

Answer 9

specificity constant

measure of enzyme performances by predicting the fate of E*S

Question 10

When is Vmax reached?

Answer 10

when the enzyme is fully saturated, [ES]= [E]T and rate equation is Vmax= Kcat[E]T

Question 11

What is the Michaelis- Menten equation?

Answer 11

Vo= Vmax [S] / Km + [S]

Question 12

What does Vo equal when [S] &laquo_space;Km

Answer 12

= (Vmax/Km) [S]

Question 13

What does Vo equal when [S] =Km

Answer 13

= Vmax/2

Question 14

What does Vo equal when [S]» Km

Answer 14

=Vmax

Question 15

A ______ enzyme would have Kcat&raquo_space; K-1 and Kcat/Km = k1

Answer 15

good

Question 16

A ______ enzyme would have Kcat &laquo_space;K-1 and Kcat/Km = 1/Km

Answer 16

poor

Question 17

What do group specific irreversible inhibitors do?

Answer 17

target a specific amino acid

Question 18

What is the specificity for active site for group specific irreversible inhibitors?

Answer 18

low

Question 19

What do substrate analogs do?

Answer 19

substrate mimic, modifies enzyme

Question 20

What is the specificity for active site for substrate analogs?

Answer 20

high

Question 21

What do suicide inhibitors do?

Answer 21

substrate mimic

unable to form products

Question 22

What is the specificity for active site in suicide inhibitors

Answer 22

very high