Lecture 13: Kinetics Flashcards
What are the three kinetic trend graphical representations that are possible?
- Linear
- Hyperbolic
- Sigmoidal
Describe the relationship between the concentration of a substrate and the effect on the rate of a zero order reaction
The changes in substrate concentration have no effect on the rate
Describe the relationship between the concentration of a substrate and the effect on the rate of a first order reaction
The changes in substrate concentration have an effect that is DIRECTLY PROPORTIONAL on the rate
If the concentration of a first order reaction doubles, what happens to the rate of that reaction?
It doubles too
Describe the relationship between the concentration of a substrate and the effect on the rate of a second order reaction
The change in concentration of the substrate will have a MAJOR effect on the rate; if it doubles, the rate will quadruple
When plotting substrate concentration vs time, which of the three order graphs is linear? (zero, first, second?)
Zero
When plotting substrate (LN)concentration vs time, which of the three order graphs is linear? (zero, first, second?)
First
When plotting substrate 1/substrate concentration vs time, which of the three order graphs is linear? (zero, first, second?)
Second
What is the equation for a first order reaction?
v=k[S]
What is the equation for a second order reaction?
v=k[S]^2 or k[A][B]
What are two commons reasons that a reaction is classified as a zero order reaction?
- if it is a unimolecular reaction
2. if the enzyme is saturated
What is the basic Michaelis Menten equation? (E and S)
E+S ES –> E+P
Define Km
Michaelis constant
[S] where the reaction rate is half maximal or where half of the active sites are full
** Find Vmax/2 on the y axis and go to the point that that correlates to on the graph and then go down to the x axis and that is your Km
Define vmax
Maximum velocity
Maximum rate possible for a given concentration of enzyme
Define Kcat
turnover number
number of substrate molecules converted per active site per time (first order constant)
Define Ks
A dissociation constant for substrate binding
What would you use if you were trying to measure an enzymes performance, or predict the fate of E*S
Kcat/Km
What is the final Michaelis Menten equation?
Vo= (Kcat [E]t [S]) / Ks + [S]
What is the equation for Vmax?
Vmax= Kcat[E]t
What is the Michaelis Menten equation when [S]<
Vo= ( vmax / Km) [S]
What is the Michaelis Menten equation when [S]=Km
Vo= Vmax / 2
What is the Michaelis Menten equation when [S]»>Km?
Vo=Vmax
When S<
First order
When S»>Km, what is the reaction order?
Zero order
Describe a “good” enzyme using Kcat and K-1(reverse reaction rate constant)
Kcat» K-1 and the specificity constant (Kcat/Km) would almost equal K1 (forward reaction rate constant)
True or False? An enzyme with multiple binding sites can follow michaelis mention as long as they are noncooperative
True
What is the equation for a line-weaver Burk plot?
(1/Vo)= (Km/Vmax) * (1/[S]o)+(1/Vmax)
What is the y intercept of a line-weaver burk graph?
1/Vmax
What is the x intercept of a line-weaver burk graph?
-1/Km
What are the three reversible inhibitors? Which two are the allosteric inhibitors?
- Competitive
- Noncompetitive
- Uncompetitive
2 and 3 are allosteric
Describe competitive inhibition in relation to vmax and Km
Vmax is constant (therefore the y intercept remains the same as the original reaction)
and Km varies, the x intercept is typically closer the origin (bigger value in THIS graph)
Describe noncompetitive inhibition in regards to Vmax and Km
Vmax is variable, so the y intercept will usually be above (lesser value on THIS graph) than the original
Km is constant, therefore the x intercept will remain the same as the original graph
Describe uncompetitive inhibition in regards to Vmax and Km
Vmax and Km are variable and the graph is usually to then left of the inhibitor graph
What does a high Km insinuate?
weak binding
What does a low Km mean?
strong binding
How does a competitive inhibitor work?
It binds to the active site, reducing the proportion of enzymes bound to a substrate
How can you offset the effects of a competitive inhibitor?
By increasing the substrate concentration
how does uncompetitive inhibition work?
It binds to the ES complex after substrate has bound
How does noncompetitive inhibition work?
inhibitor and substrate bind at the same time at different sites, decreasing the amount of functional enzymes instead of the proportions of the E and S
What do group specific inhibitors do?
They have a low affinity for the active site and they target a specific amino acid in order to inactivate the entire enzyme
What is an example of a group specific enzyme?
DIPF- targets serine
What do substrate specific analogs do?
They have a high affinity for the active site by mimicking the substrate and modifying the enzyme
What is an example of a substrate analog and what does it effect?
TPCK effects chymotrypsin by looking like Phe
What do suicide inhibitors do?
They have a very high affinity for the activate site by looking like the substrate, they bind to the enzyme and cause a series of reactions that cause the enzyme to become inactive
What are the assumptions of the Michaelis Menten equation?
Assumes that the binding of the substrate is at equilibrium
and assumes that when
[S]»_space; [E] then the change in S is 0
If you were in the lab, and you had a reaction where the Km is significantly greater than the concentration of your substrate, what order of reaction would you be dealing with?
First order
BTLO: Create real world hypothetical scenarios for the 6 different inhibitors…
COMPETITIVE INHIBITOR
Bind at the same active site; cabs in New york; everyone wants the same cabs; and if you increase the number of cabs (some people are the enzymes and others are the substrates but idk it sorta works)
BTLO: Create real world hypothetical scenarios for the 6 different inhibitors…
UNCOMPETITIVE
inhibitor binds to the complex after the substrate and enzyme have bound….
STI transmission happens once the penis is in the vagina….?
BTLO: Create real world hypothetical scenarios for the 6 different inhibitors…
NONCOMPETITIVE
inhibitor and substrate can bind simultaneously
nongender neutral bathrooms
mem (inhibitor) and women (substrate) can both go to the bathroom (enzyme) cat the same time
BTLO: Create real world hypothetical scenarios for the 6 different inhibitors…
GROUP SPECIFIC
reacts with a certain group of amino acids
Liberals and conservatives usually always interact… and react to each other
BTLO: Create real world hypothetical scenarios for the 6 different inhibitors…
AFFINITY LABELS
structurally similar to the substrate (mimics) and is able to bind
Mrs. Doubtfire. She was structurally similar to the dad (except in disguise) and mimics what the mom wants, and is able to BOND with the kids, which is what Robin Williams wanted…?
BTLO: Create real world hypothetical scenarios for the 6 different inhibitors…
SUICIDE INHIBITORS
substrate mimic’s but is not able to make products
The stars who are making their kids look appealing to colleges, ie mimicking the type of student that the university wants, except these kids aren’t smart enough to do it on their own, so they probably aren’t smart enough to make results (products) ((that’s a stretch, sorry)
