Kinetics

Question 1

What are the 3 possible kinetic trends?

Answer 1

Linear
Hyperbolic
Sigmoidal

Question 2

What are the reaction orders for irreversible reactions

Answer 2

Zeroth order- no substrates are needed for the reaction to form a product. This could be because there are already enough substrates to saturate the enzymes.
1st order- one substrate going to a product
2nd order- 2 substrates going to a product

Question 3

Describe the graph for zeroth order

Answer 3

y-axis has [S]

Substrate-independent interpretations:
A) Unimolecular reaction
B) Enzyme is saturated

Question 4

Describe the graph for 1st order

Answer 4

ln [S]

Question 5

Describe the graph for 2nd order

Answer 5

1/[S]

Question 6

Describe reversible reactions

Answer 6

At equilibrium, the forward rate is equal to the reverse rate

The substrate is being both used and created

Question 7

For reversible reactions, explain K_A and K_D?

Answer 7

K_A= the association constant (make the product)

K_D= the dissociation constant (unmake the product)

Question 8

Michaelis Menten enzymes follow ____ _____ Kinetics

Answer 8

First Order

Question 9

_______ is not a first order reaction

Answer 9

Catalysis

Question 10

Define the variable Km and what is its name?

Answer 10

Michaelis Constant

[S] where the reaction rate is half maximal OR half of the active sites are full (similar to cooperativity)

It describes what happens to the ES complex: Km=[E][S]/[ES]

Question 11

Define the variable Vmax and what is its name?

Answer 11

Maximum velocity

Maximum rate possible for a given concentration of enzyme

Question 12

Define the variable Kcat and what is its name?

Answer 12

Turnover Number

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

Question 13

Define the variable Ks and what is its name?

Answer 13

N/A

Dissociation constant for substrate binding

Question 14

Define the variable Kcat/Km and what is its name?

Answer 14

Specificity Constant

The measure of enzyme performance (efficiency) by predicting the fate of the Enzyme-Substrate complex

Question 15

When in the laboratory, what is something we cannot measure and how do we get around this problem?

Answer 15

We cannot measure [E] (free enzyme)

The solution is to know how much enzyme you added to the reaction ([E]_T)- this stands for the total enzyme.

Then you use this equation to find the amount of free enzyme:
[E]= [E_T] - [ES]

Question 16

What are the 4 equations we are supposed to know?

Answer 16

[ES]=[ET}[S]/Ks + [S]

Vo=Kcat [ET] [S]/ Ks + [S]

Vmax=Kcat [ET]

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

Question 17

Describe the three laboratory conditions that are very important and list their corresponding vo

Answer 17

[S] < Km Vo=Vmax/Km

[S]=Km Vo=Vmax/2

[S] > Km Vo=Vmax *This method is the most used in the labs

Question 18

For the specificity constant, Kcat/Km, describe the conditions of a good enzyme and a poor enzyme

Answer 18

1. A good enzyme would have Kcat>K_-1 (K_-1=reactants forming) and Kcat/Km=K1 (products forming)
2. A poor enzyme would have Kcat< K_-1 and Kcat/Km=1/Km

Question 19

Multiple binding sites can follow Michaelis Menten kinetics, as long as they are __________

Answer 19

Noncooperative

This means they have a hyperpbolic curve on the reaction rate. If it is a cooperative enzyme then the reaction curve will be sigmoidal

Question 20

What are the 2 types of inhibitors?

Answer 20

Irreversible- bind using covalent interactions

Reversible- bind using noncovalent interactions

Question 21

What are the 3 types of reversible inhibitors?

Answer 21

Competitive
Noncompetitive- Allosteric
Uncompetitive- Allosteric

Question 22

Describe the Lineweaver Burke plot for competitive inhibitors

Answer 22

Vmax is constant

Km increases

Question 23

Describe the Lineweaver Burke plot for noncompetitive inhibitors

Answer 23

Vmax decreases

Km is constant

Question 24

Describe the Lineweaver Burke plot for uncompetitive inhibitors

Answer 24

Both Vmax and Km decreases

Question 25

What are the 3 types of irreversible inhibitors and what does each do? Describe each one’s specificity for the active site.

Answer 25

Group Specific- Target a specific amino acid. Low specificity for the active site.

Substrate Analogs- Mimics the substrate, modifies the enzyme. High specificity for the active site.

Suicide Inhibitors- Mimics the substrate, unable to form products. Very High specificity for the active site.

Question 26

What are the textbook example for group-specific irreversible inhibitors

Answer 26

DIPF targets Serines

Question 27

What are the textbook example for substrate analogs irreversible inhibitors

Answer 27

TPCK looks like Phe to chymotrypsin

Question 28

What are the textbook example for suicide inhibitors irreversible inhibitors

Answer 28

N,N- Dimethylproparyglamine inactivates FAD