Kinetics Flashcards
What are the 3 possible kinetic trends?
Linear
Hyperbolic
Sigmoidal
What are the reaction orders for irreversible reactions
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
Describe the graph for zeroth order
y-axis has [S]
Substrate-independent interpretations:
A) Unimolecular reaction
B) Enzyme is saturated
Describe the graph for 1st order
ln [S]
Describe the graph for 2nd order
1/[S]
Describe reversible reactions
At equilibrium, the forward rate is equal to the reverse rate
The substrate is being both used and created
For reversible reactions, explain K_A and K_D?
K_A= the association constant (make the product)
K_D= the dissociation constant (unmake the product)
Michaelis Menten enzymes follow ____ _____ Kinetics
First Order
_______ is not a first order reaction
Catalysis
Define the variable Km and what is its name?
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]
Define the variable Vmax and what is its name?
Maximum velocity
Maximum rate possible for a given concentration of enzyme
Define the variable Kcat and what is its name?
Turnover Number
Number of substrate molecules converted per active site per time (first-order rate constant)
Define the variable Ks and what is its name?
N/A
Dissociation constant for substrate binding
Define the variable Kcat/Km and what is its name?
Specificity Constant
The measure of enzyme performance (efficiency) by predicting the fate of the Enzyme-Substrate complex
When in the laboratory, what is something we cannot measure and how do we get around this problem?
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]
What are the 4 equations we are supposed to know?
[ES]=[ET}[S]/Ks + [S]
Vo=Kcat [ET] [S]/ Ks + [S]
Vmax=Kcat [ET]
Vo= Vmax [S]/ Ks + [S]
Describe the three laboratory conditions that are very important and list their corresponding vo
[S] < Km Vo=Vmax/Km
[S]=Km Vo=Vmax/2
[S] > Km Vo=Vmax *This method is the most used in the labs
For the specificity constant, Kcat/Km, describe the conditions of a good enzyme and a poor enzyme
- A good enzyme would have Kcat>K_-1 (K_-1=reactants forming) and Kcat/Km=K1 (products forming)
- A poor enzyme would have Kcat< K_-1 and Kcat/Km=1/Km
Multiple binding sites can follow Michaelis Menten kinetics, as long as they are __________
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
What are the 2 types of inhibitors?
Irreversible- bind using covalent interactions
Reversible- bind using noncovalent interactions
What are the 3 types of reversible inhibitors?
Competitive
Noncompetitive- Allosteric
Uncompetitive- Allosteric
Describe the Lineweaver Burke plot for competitive inhibitors
Vmax is constant
Km increases
Describe the Lineweaver Burke plot for noncompetitive inhibitors
Vmax decreases
Km is constant
Describe the Lineweaver Burke plot for uncompetitive inhibitors
Both Vmax and Km decreases
What are the 3 types of irreversible inhibitors and what does each do? Describe each one’s specificity for the active site.
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.
What are the textbook example for group-specific irreversible inhibitors
DIPF targets Serines
What are the textbook example for substrate analogs irreversible inhibitors
TPCK looks like Phe to chymotrypsin
What are the textbook example for suicide inhibitors irreversible inhibitors
N,N- Dimethylproparyglamine inactivates FAD
