Lecture 13 Flashcards
What are the 3 ways you should graph your data in order to determine the reaction order of the reaction?
(the following are all Y axis values and are plotted with the X axis representing time)
[S]
ln[S]
1/[S]
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?
the linear line identifies the reaction order of the data
the K value is the slope of the line
For first order kinetics, describe y axis equation for the line that is expected to be linear and state the what V=
Y axis: ln[S]
v = k[S]
For second order kinetics, describe y axis equation for the line that is expected to be linear and state the what V=
Y Axis: 1/[S]
v = k[Sa][Sb]
For Zero order kinetics, describe y axis equation for the line that is expected to be linear and state the what V=
Y axis: [S]
v = k
For first order kinetics, state the relationship between the substrate(s) and the product(s)
1 S –> P
For second order kinetics, state the relationship between the substrate(s) and the product(s)
2 S –> P
2 different substrates?
For Zero order kinetics, state the relationship between the substrate(s) and the product(s)
S –> P
state the 2 criteria of a zero order reaction that are unique to it
- it is a unimolecular reaction
2. the enzyme is saturated
State the type of reversible inhibition that has a constant Vmax and a variable Km. THEN state what it’s graph looks like.
Competitive: forms a steeper slope that intersects with the uninhibited plot at the Y axis
(competitive chopsticks)
State the type of reversible inhibition that has a variable Vmax and a constant Km. THEN state what it’s graph looks like.
Noncompetitive: forms a steeper slope that intersects with the uninhibited plot at the x axis
(“nom nom” noncompetitive)
State the type of reversible inhibition that has a variable Vmax and a variable Km. THEN state what it’s graph looks like.
Uncompetitive: has the same slope as the uninhibited plot but does not intersect with it
(UNcompetitive is UNassociated with the slope)
Which of the 3 reversible inhibition types are considered to be “Allosteric inhibitors”?
Noncompetitive
Uncompetitive
what are the assumptions and conditions needed to use the michaelis-Menten equation? (3 of these)
- The binding of the substrate to the enzyme is at equilibrium
So Ks = (K-1/K1) - 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 - 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
Define Km in words and mathematical equations
Michaelis Constant
Km: the [S] or concentration of the substrate that reaches half of the maximal reaction rate for a specific reaction
Define Vmax in words and mathematical equations
Maximum velocity
Vmax: the maximum rate possible for a given concentration of enzyme
Define Kcat in words and mathematical equations
Turnover number
Kcat: Number of substrate molecules converted per active site per time (first order rate constant)
Define KS in words and mathematical equations
(NOT like the Kd dissociation constant for the products)
A dissociation constant for the substrate that is binding
Define Kcat/Km in words and mathematical equations
Specificity constant
Measure of enzyme performance by predicting the fate of E*S
Describe how to create a Lineweaver-Burk plot (state equation for it)
It is a y = mx + b style equation
y = 1/V0
m = Km/Vmax
x = 1/[S]0
b = 1/Vmax
Describe what each data point on a lineweaver-burk plot represents
each data point represents an individual kinetic assay
Describe how to determine an inhibitor mechanism from a Lineweaver-Burk plot
graph it 3 ways and use the linear lineweaver-burk plot to determine the order of the reaction
What is the reaction rate (v) value of a reaction at equilibrium?
0
No matter what, catalysis is a ____ ______ reaction
first order
A good enzyme would have ______ and Kcat/Km would equal what?
Kcat»_space; K-1
Kcat/Km = K1
describes the enzyme-substrate complex formation
A bad enzyme would have ______ and Kcat/Km would equal what?
Kcat «_space;K-1
Kcat/KM = 1/Km
describes the dissociation of the enzyme-substrate complex
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?
Noncooperative
The graph would be hyperbolic
(a cooperative reaction would NOT follow michaelis menten kinetics and would yield a sigmoidal curve)
What is a double reciprocal plot?
a lineweaver-burk plot
Double reciprocal plot = lineweaver-burk plot
For the following irreversible inhibitor, state what it does and the level of specificity it has for the active site.
Group-Specific:
Group-specific irreversible inhibitors target a specific AA
They have a low affinity for the active site
For the following irreversible inhibitor, state what it does and the level of specificity it has for the active site.
Substrate Analogs:
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
For the following irreversible inhibitor, state what it does and the level of specificity it has for the active site.
Suicide Inhibitors:
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
State which 2 forms of irreversible inhibitor mechanisms employ the use of substrate mimicking.
Substrate analogs
Suicide inhibitors
Define V(sub)0
initial velocity of a reaction
Define K(sub)D
dissociation constant for products in a REVERSIBLE reaction
product becomes the reactant
(Ks is the dissociation constant for enzyme binding to reactants)
