Deck 7: Kinetics and Regulation

Question 1

The y-intercept of a Lineweaver-Burk plot is ____________.

Answer 1

1/V0

Question 2

An allosteric ______________ stabilizes the T state of the enzyme.

Answer 2

inhibitor

Question 3

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
At _______________, there is no net change in the concentration of substrate or product.

Answer 3

h

Question 4

The type of inhibition by a product of one enzyme on another enzyme in an earlier protein in a metabolic pathway is considered a(an) ______________ inhibitor.

Question 5

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
_______________: Enzymes that do not obey Michaelis-Menten kinetics.

Question 6

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
The kcat is often referred to as the _______________.

Question 7

______________ is directly dependent on enzyme concentration.

Question 8

Allosteric enzymes can be identified because the plot of initial velocity, V0, versus substrate concentration, S, is not hyperbolic but ______________ shaped.

Question 9

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
An enzyme's affinity for its substrate is measured by the _______________ constant.

Question 10

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
_______________: The study of rates of chemical reactions.

Question 11

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
______________: Experiments that determine the kinetics of a population of enzyme molecules.

Question 12

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
_______________: A complex array of enzyme reactions organized in multiple pathways.

Question 13

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
The value V0 is called the _______________.

Question 14

Reactions that have more two reactants or substrates are considered ______________ reactions.

Question 15

One way to measure the rate of an enzymatic reaction is to measure the loss of ______________ over time.

Question 16

The ______________ rule states that all subunits in an allosteric enzyme must be in either the T or the R state; there can not be hybrids.

Question 17

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
A reaction that is directly proportional to the concentration of reactant is a(n) ______________.

Question 18

An enzyme will be most sensitive to changes in cellular concentration when the concentration is ______________.

Question 19

The Michaelis-Menten model assumes that ______________ is the rate constant ignored because producthas not accumulated.

Question 20

Use the following to answer questions
Choose the correct answer from the list below. Not all of the answers will be used.
a) first-order reaction
b) second-order reaction
c) metabolism
d) ensemble
e) biomolecular
f) turnover number
g) Michaelis-Menten
h) equilibrium
i) bsequentialj) kinetics
k) initial velocity
l) allosteric
m) ping-pong
A reaction with two substrates is considered a(n) _______________ reaction.

Question 21

The rate of a reaction is dependent on [ES]. Using an enzyme-catalyzed reaction scheme, Equation (6) p. 107, describe the kinetic model for [ES].

Question 22

The formula V0 = Vmax [S] , indicates the relationship between
[S] + KM

A) the enzyme activity and the equilibrium constant.
B) the rate of a catalyzed reaction and the equilibrium constant.
C) enzyme activity as a function of substrate concentration.
D) All of the above.
E) None of the above.

Question 23

The model describing allosteric regulation that requires all subunits to be in the same state is called the:

A) concerted model.
B) syncopated model.
C) cooperative model.
D) equilibrium model.
E) None of the above.

Question 24

A protease hydrolyzes the peptide backbone. What is/are the substrate(s) and product for this reaction? Assuming that the concentration of water is so high (~55M) that it does not appreciably change, to what kind of reaction order would one assign this reaction?

Question 25

Allosteric modifiers alter the equilibria between:

A) the ES state.
B) the R and T forms of a protein.
C) the forward and reverse reaction rate.
D) the formation of a product and its reverse reaction.
E) All of the above.

Question 26

Allosteric effectors:

A) can cause large changes in enzymatic activity.
B) can lead to a decrease in the availability of a protein.
C) do not alter the sensitivity of a metabolic pathway.
D) decrease the sensitivity of the enzyme at nearly all concentrations of substrate.
E) alter enzyme activity by binding to the active site of an enzyme.

Question 27

Given are five KM values for the binding of substrates to a particular enzyme. Which has the strongest affinity when k−1 is greater than k2?

A) 150 mM
B) 0.15 mM
C) 150 M
D) 1.5 nM
E) 15,000 pM

Question 28

When [S] << KM, the enzymatic velocity depends on:

A) the values of kcat/KM, [S], and [E]t.
B) the Vmax of the reaction.
C) the affinity of the substrate for the catalytic site.
D) kcat.
E) the formation of the ES complex.

Question 29

What does Vmax indicate?

Question 30

Which of the following is true under these conditions: The enzyme concentration is 5 nM, the substrate concentration is 5 mM, and the KM is 5 M.

A) The enzyme is saturated with substrate.
B) Most of the enzyme does not have substrate bound.
C) There is more enzyme than substrate.
D) All of the above.
E) None of the above.

Question 31

Loss of allosteric regulation in the production of purine nucleotides results in:

A) excess nucleotides for DNA.
B) loss of RNA due to ribose phosphate synthetase.
C) decreased urate degradation.
D) loss in urate concentration.
E) None of the above.

Question 32

Allosteric proteins:

A) contain distinct regulatory sites and have multiple functional sites.
B) display cooperativity.
C) always consist of several identical subunits.
D) A and B.
E) A, B, and C.

Question 33

What value of [S], as a fraction of KM, is required to obtain 20% Vmax? [S] equals:

A) 0.2 KM
B) 0.25 KM
C) 0.5 KM
D) 0.75 KM
E) 0.8 KM

Question 34

When a substrate concentration is much greater than KM, the rate of catalysis is almost equal to:

A) KD
B) kcat.
C) Vmax.
D) All of the above.
E) None of the above.

Question 35

The KM is:

A) equal to the product concentration at initial reaction conditions.
B) equal to the substrate concentration when the reaction rate is half its maximal value.
C) proportional to the standard free energy.
D) All of the above.
E) None of the above.

Question 36

Homotrophic effects of allosteric enzymes:

A) are due to the effects of substrates.
B) are due to the effects of allosteric activators.
C) shift the kinetics curve to the left.
D) shift the kinetics curve to the right.
E) None of the above.

Question 37

What is the Michaelis-Menten equation? Define all parameters.

Question 38

Multiple substrate enzyme reactions are divided into two classes:

A) sequential displacement and double displacement.
B) double displacement and concerted displacement.
C) sequential displacement and concerted displacement.
D) A and C.
E) None of the above.

Question 39

A critical feature of the Michaelis-Menten model of enzyme catalysis is:

A) increasing the probability of product formation.
B) shifting the reaction equilibrium.
C) the formation of an ES complex.
D) All of the above.
E) None of the above.

Question 40

In many enzyme assays, the natural substrate and product are not used. Why?

Question 41

Describe the difference between the concerted and the sequential model of allosteric regulation.

Question 42

When designing a drug to inhibit the formation of a product which requires several enzymes in a metabolic pathway, what should be the first piece of information a biochemist needs to develop the drug?

Question 43

What is the turnover number for an enzyme and what does this value tell us about the enzyme?

Question 44

Would you expect the order of substrate binding to be critical for enzyme catalysis?

Question 45

How does the sequential model differ from the concerted model for allosteric enzymes?

Question 46

How do the intermediate steps in multisubstrate enzyme mechanisms differ?

Question 47

What is the upper limit of kcat/KM?