Lecture 13

Question 1

What are the 3 ways you should graph your data in order to determine the reaction order of the reaction?

Answer 1

(the following are all Y axis values and are plotted with the X axis representing time)

[S]

ln[S]

1/[S]

Question 2

Once you have graphed your data one of the 3 ways, which line identifies the reaction order? what value represents the slope of the line?

Answer 2

the linear line identifies the reaction order of the data

the K value is the slope of the line

Question 3

For first order kinetics, describe y axis equation for the line that is expected to be linear and state the what V=

Answer 3

Y axis: ln[S]

v = k[S]

Question 4

For second order kinetics, describe y axis equation for the line that is expected to be linear and state the what V=

Answer 4

Y Axis: 1/[S]

v = k[Sa][Sb]

Question 5

For Zero order kinetics, describe y axis equation for the line that is expected to be linear and state the what V=

Answer 5

Y axis: [S]

v = k

Question 6

For first order kinetics, state the relationship between the substrate(s) and the product(s)

Answer 6

1 S –> P

Question 7

For second order kinetics, state the relationship between the substrate(s) and the product(s)

Answer 7

2 S –> P

2 different substrates?

Question 8

For Zero order kinetics, state the relationship between the substrate(s) and the product(s)

Answer 8

S –> P

Question 9

state the 2 criteria of a zero order reaction that are unique to it

Answer 9

1. it is a unimolecular reaction

2. the enzyme is saturated

Question 10

State the type of reversible inhibition that has a constant Vmax and a variable Km. THEN state what it’s graph looks like.

Answer 10

Competitive: forms a steeper slope that intersects with the uninhibited plot at the Y axis
(competitive chopsticks)

Question 11

State the type of reversible inhibition that has a variable Vmax and a constant Km. THEN state what it’s graph looks like.

Answer 11

Noncompetitive: forms a steeper slope that intersects with the uninhibited plot at the x axis
(“nom nom” noncompetitive)

Question 12

State the type of reversible inhibition that has a variable Vmax and a variable Km. THEN state what it’s graph looks like.

Answer 12

Uncompetitive: has the same slope as the uninhibited plot but does not intersect with it
(UNcompetitive is UNassociated with the slope)

Question 13

Which of the 3 reversible inhibition types are considered to be “Allosteric inhibitors”?

Answer 13

Noncompetitive

Uncompetitive

Question 14

what are the assumptions and conditions needed to use the michaelis-Menten equation? (3 of these)

Answer 14

1. The binding of the substrate to the enzyme is at equilibrium
   So Ks = (K-1/K1)
2. Since we are assuming initial rate, not enough product is present for the reverse reaction to occur
   So we can ignore the E*P species
3. The steady state assumption: when [S] is very large, DeltaS = 0 (bc an appreciable amount of substrate is not going to be converted into product)
   So the dissociation constant (Km) = (K-1 + K2)/K1

Question 15

Define Km in words and mathematical equations

Answer 15

Michaelis Constant

Km: the [S] or concentration of the substrate that reaches half of the maximal reaction rate for a specific reaction

Question 16

Define Vmax in words and mathematical equations

Answer 16

Maximum velocity

Vmax: the maximum rate possible for a given concentration of enzyme

Question 17

Define Kcat in words and mathematical equations

Answer 17

Turnover number

Kcat: Number of substrate molecules converted per active site per time (first order rate constant)

Question 18

Define KS in words and mathematical equations

Answer 18

(NOT like the Kd dissociation constant for the products)

A dissociation constant for the substrate that is binding

Question 19

Define Kcat/Km in words and mathematical equations

Answer 19

Specificity constant

Measure of enzyme performance by predicting the fate of E*S

Question 20

Describe how to create a Lineweaver-Burk plot (state equation for it)

Answer 20

It is a y = mx + b style equation

y = 1/V0

m = Km/Vmax

x = 1/[S]0

b = 1/Vmax

Question 21

Describe what each data point on a lineweaver-burk plot represents

Answer 21

each data point represents an individual kinetic assay

Question 22

Describe how to determine an inhibitor mechanism from a Lineweaver-Burk plot

Answer 22

graph it 3 ways and use the linear lineweaver-burk plot to determine the order of the reaction

Question 23

What is the reaction rate (v) value of a reaction at equilibrium?

Answer 23

0

Question 24

No matter what, catalysis is a ____ ______ reaction

Answer 24

first order

Question 25

A good enzyme would have ______ and Kcat/Km would equal what?

Answer 25

Kcat&raquo_space; K-1

Kcat/Km = K1
describes the enzyme-substrate complex formation

Question 26

A bad enzyme would have ______ and Kcat/Km would equal what?

Answer 26

Kcat &laquo_space;K-1

Kcat/KM = 1/Km
describes the dissociation of the enzyme-substrate complex

Question 27

Multiple binding site reactions CAN follow michaelis menten kinetics as long as they are _____. What type of graph would be observed if it’s y axis was reaction rate and the x axis was [S] and the reaction was a multiple binding site reaction that followed michaelis menten kinetics?

Answer 27

Noncooperative

The graph would be hyperbolic
(a cooperative reaction would NOT follow michaelis menten kinetics and would yield a sigmoidal curve)

Question 28

What is a double reciprocal plot?

Answer 28

a lineweaver-burk plot

Double reciprocal plot = lineweaver-burk plot

Question 29

For the following irreversible inhibitor, state what it does and the level of specificity it has for the active site.

Group-Specific:

Answer 29

Group-specific irreversible inhibitors target a specific AA

They have a low affinity for the active site

Question 30

For the following irreversible inhibitor, state what it does and the level of specificity it has for the active site.

Substrate Analogs:

Answer 30

Substrate analog irreversible inhibitors modify the enzyme in such a way that the reaction can no longer form the products

They have a high affinity for the active site

Question 31

For the following irreversible inhibitor, state what it does and the level of specificity it has for the active site.

Suicide Inhibitors:

Answer 31

Suicide inhibitor irreversible inhibitors modify the substrate in such a way that the reaction can no longer form products

They have a very high affinity for the active site

Question 32

State which 2 forms of irreversible inhibitor mechanisms employ the use of substrate mimicking.

Answer 32

Substrate analogs

Suicide inhibitors

Question 33

Define V(sub)0

Answer 33

initial velocity of a reaction

Question 34

Define K(sub)D

Answer 34

dissociation constant for products in a REVERSIBLE reaction

product becomes the reactant
(Ks is the dissociation constant for enzyme binding to reactants)