Ch. 12 Quiz Question

A compound that distorts the active site, rendering the enzyme catalytically inactive is called A: a uncompetitive inhibitor B: an allosteric effector C: an inactivator D: a competitive inhibitor E: none of the above

A

A new drug has been discovered which inhibits the reaction catalyzed by enzyme A. Based on the information shown below, what is this drug? A: competitive inhibitor B: uncompetitive inhibitor C: mixed inhibiton D: allosteric activator E: More information is required to answer the question.

A

From the graph below plotting data that was collected under steady state conditions, velocity on the y-axis in units of μM/s and substrate concentration of the x-axis in units of μM, what is the Vmax? A: 0.24 μM/s B: 18 μM C: 0.2 μM D: 0.24 μM E: 0.12 μM/s

A

In the plot below, can the KM be determined? If so, what is its value? A: Yes, it is 30 mM. B: Yes, it is 30 mM/sec. C: Yes, it is 60 mM/sec D: Yes, it is 60 mM E: No this data does not follow Michaelis-Menten kinetics

A

Irreversible enzyme inhibitors A: inactivate the enzyme. B: inhibit competitively. C: maximize product by minimizing ES → E+S. D: behave allosterically. E: function via Ping Pong mechanism.

A

Km A: is the concentration of substrate where the enzyme achieves ½Vmax. B: is equal to Ks. C: measures the stability of the product D: is high if the enzyme has high affinity for the substrate. E: All of the above are correct.

A

The Michaelis constant KM is defined as: T/F A: (k-1 + k2)/ k1 B: ½ Vmax C: [S] = [ES] D: [ES]/2

A: T B: F C: F D: F

Enzyme activity in cells is controlled by which of the following? T/f A: covalent modifications B: modulation of expression of levels C: feedback inhibition D: allosteric effectors

A: T B: T C: T D: T

An enzyme is near maximum efficiency when A: its turnover number is near Vmax. B: kcat/KM is near 108 M-1s-1. C: k1 << k-1. D: kcat/KM is equal to kcat. E: KM is large when k2 exceeds k1.

B

At substrate concentrations much lower than the enzyme concentration, A: the rate of reaction is expected to be inversely proportional to substrate concentration. B: the rate of reaction is expected to be directly proportional to substrate concentration. C: first order enzyme kinetics are not observed. D: the KM is lower. E: the rate of reaction is independent of substrate concentration.

B

Find kcat for a reaction in which Vmax is 4 × 10-4 mol·min-1 and the reaction mixture contains one microgram of enzyme (the molecular weight of the enzyme is 200,000 D). A: 2 × 10-11 min-1 B: 8 × 107 min-1 C: 8 × 109 min-1 D: 2 × 10-14 min-1 E: 4 × 108 min-1

B

Find the initial velocity for an enzymatic reaction when Vmax = 6.5 × 10-5 mol·sec-1, [S] = 3.0 × 10-3 M, KM = 4.5 × 10-3 M and the enzyme concentration at time zero is 1.5 × 10-2 μM. A: 3.9 × 10-5 mol·sec-1 B: 2.6 × 10-5 mol·sec-1 C: 1.4 × 10-2 mol·sec-1 D: 8.7 × 10-3 mol·sec-1 E: Not enough information is given to make this calculation.

B

Following several experiments, the data presented on the graph below was obtained. What can you determine from this graph? A: This data may have been collected both in the absence (solid line) and presence (dashed line) of a competitive inhibitor. B: This data may have been collected both in the absence (solid line) and presence (dashed line) of a mixed (noncompetitive) inhibitor. C: This data may have been collected both in the absence (solid line) and presence (dashed line) of mechanism based inhibitor. D: This data may have been collected both in the absence (solid line) and presence (dashed line) of an inhibitor which binds the active site. E: More than one of the above are correct.

B

From the graph below plotting data that was collected under steady state conditions, velocity on the y-axis in units of μM/s and substrate concentration of the x-axis in units of μM, what is the KM? A: 0.24 μM/s B: 18 μM C: 0.2 μM D: 0.24 μM E: 0.12 μM/s

B

I propose to design a new drug which will act as an inhibitor for an enzyme. If I have used all current information about the mechanism of this enzyme to design this inhibitor and I carefully engineer it with similar chemical properties of the transition state, what type of inhibitor am I attempting to engineer and how will I know if I have succeeded? A: A competitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in Vmax. B: A competitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in KM. C: A uncompetitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in KM. D: A uncompetitive inhibitor, collect kinetic data both in the presence and absence of inhibitor and watch for a change in Vmax. E: None of the above.

B

Which of the following is correct in regards to the diagram below? A: X=A, Y=B, Z=P B: X=B, Y=A, Z=Q C: X=E, Y=A, Z=E D: X=E, Y=B, Z=Q E: X=E, Y=B, Z=P

B

A lead compound would be most promising if it had: A: KI = 4.7 × 105 M. B: KI = 1.5 × 108 M. C: KI = 1.5 × 10-8 M. D: KI = 4.7 × 10-5 M. E: KM = 4.7 × 105 M.

C

Based on the figures below, which of the following expressions would correctly define KM? A: A= KM B: KM = A/2 C: B = KM D: C = - KM E: D= 1/ KM

C

Diagram refers to a (an) A: Ping Pong reaction. B: ordered bisubstrate reaction. C: random bisubstrate reaction. D: double order ping pong reaction. E: X, Y, and Z must be provided in order to answer correctly.

C

Protein kinases are involved in A: the digestion of drugs to potentially toxic byproducts. B: the degradation of enzymes to the component amino acids. C: the phosphorylation of a wide variety of proteins. D: the metabolism of drugs to water soluble, excretable compounds. E: all of the above

C

When [S] = KM, ν0 = (_____)× (Vmax). A: [S] B: 0.75 C: 0.5 D: KM E: kcat

C

________ clinical trials are focused on evaluating the efficacy of new drug candidates, and usually use _____ test. A: Phase 1; single blind B: Phase 1; double blind C: Phase 2; single blind D: Phase 2; double blind E: Phase 3; double blind

C

A two-substrate enzymatic reaction in which one product is produced before the second substrate binds to the enzyme has a ______ mechanism. A: isozymes B: [A] C: the rate constant D: Ping Pong E: bimolecular F: ES complex G: random ordered H: unimolecular I: [A]2 J: competitive inhibition K: phosphorylation L: small KS M: large KS N: uncompetitive inhibition O: [B]

D

Based on the figures below, which of the following expressions would be correct? A: Vmax = 1/B B: C = 1/ Vmax C: D= Vmax D: D = 1/ Vmax E: A = 1/ Vmax

D

Determine the KM and Vmax from the following graph. (Note: On the x-axis the minor tick mark spacing is 0.005; on the y-axis the minor tick mark spacing is 0.002). A: KM = [0.006]; Vmax = 0.0075/s B: KM = [0.196]; Vmax = 0.0075/s C: KM = [165]; Vmax = 33/s D: KM = [33]; Vmax = 167/s E: KM = [270]; Vmax = 68/s

D

The KM can be considered to be the same as the dissociation constant KS for E + S binding if A: the concentration of [ES] is unchanged. B: ES → E + P is fast compared to ES → E + S. C: k1 >> k2. D: k2 << k-1. You got it right E: this statement cannot be completed because KM can never approximate KS.

D

What is the velocity of a first-order reaction at 37oC when the reactant concentration is 6 × 10^-2 M and the rate constant is 8 × 10^3 sec-1? A: 1.33 × 105 M-1·sec-1 B: 1.33 × 105 M·sec C: 7.5 × 10-2 M·sec D: 4.8 × 102 M·sec-1 E: Not enough data are given to make this calculation

D

For the reaction, the steady state assumption A: implies that k1=k−1 B: implies that k−1 and k2 are such that the [ES] = k1[ES] C: [P]>>[E] D: [S] = [P] E: ES breakdown occurs at the same rate as ES formation

E

In uncompetitive inhibition, the inhibitor binds only to the ______. A: isozymes B: [A] C: the rate constant D: Ping Pong E: bimolecular F: ES complex G: random ordered H: unimolecular I: [A]2 J: competitive inhibition K: phosphorylation L: small KS M: large KS N: uncompetitive inhibition O: [B]

F

The type of enzyme inhibition in which Vmax is unaffected is ______ A: isozymes B: [A] C: the rate constant D: Ping Pong E: bimolecular F: ES complex G: random ordered H: unimolecular I: [A]2 J: competitive inhibition K: phosphorylation L: small KS M: large KS N: uncompetitive inhibition O: [B]

J

A common type of covalent modification of regulatory enzymes involves ______ of serine residues. A: isozymes B: [A] C: the rate constant D: Ping Pong E: bimolecular F: ES complex G: random ordered H: unimolecular I: [A]2 J: competitive inhibition K: phosphorylation L: small KS M: large KS N: uncompetitive inhibition O: [B]

K

Compounds that function as "mixed inhibitors: T/F Interfere with substrate binding to the enzyme T/F bind to the enzyme reversibly T/F can bind to the enzyme/substtrate complex

T T T