Lecture 13: Kinetics Flashcards by Tori Tyler

What are the three kinetic trend graphical representations that are possible?

Linear
Hyperbolic
Sigmoidal

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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

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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

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If the concentration of a first order reaction doubles, what happens to the rate of that reaction?

It doubles too

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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

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When plotting substrate concentration vs time, which of the three order graphs is linear? (zero, first, second?)

Zero

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When plotting substrate (LN)concentration vs time, which of the three order graphs is linear? (zero, first, second?)

First

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When plotting substrate 1/substrate concentration vs time, which of the three order graphs is linear? (zero, first, second?)

Second

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What is the equation for a first order reaction?

v=k[S]

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What is the equation for a second order reaction?

v=k[S]^2 or k[A][B]

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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

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What is the basic Michaelis Menten equation? (E and S)

E+S ES –> E+P

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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

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Define vmax

Maximum velocity

Maximum rate possible for a given concentration of enzyme

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Define Kcat

turnover number

number of substrate molecules converted per active site per time (first order constant)

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Define Ks

A dissociation constant for substrate binding

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What would you use if you were trying to measure an enzymes performance, or predict the fate of E*S

Kcat/Km

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What is the final Michaelis Menten equation?

Vo= (Kcat [E]t [S]) / Ks + [S]

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What is the equation for Vmax?

Vmax= Kcat[E]t

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What is the Michaelis Menten equation when [S]<

Vo= ( vmax / Km) [S]

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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?

1. Competitive 2. Noncompetitive 3. 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] >> [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)