1. A sigmoidal plot of substrate concentration ([S]) verses reaction velocity (V) may indicate: (A) Michaelis-Menten kinetics (C) Competitive inhibition 2. The kinetic effect of purely competitive inhibitor of an enzyme: (A) Increases K without affecting Vma (B) Decreases K, without affecting Vmas (C) Increases Vma without affecting K (D) Decreases Vmas without affecting Km 3. In reversible non-competitive enzyme activity inhibition: (A) Vma is increased (C) Vma, is decreased (B) Co-operative binding (D) Non-competitive inhibition (B) K is increased (D) Concentration of active enzyme is reduced

1. A sigmoidal plot of substrate concentration ([S]) verses reaction velocity (V) may indicate: (A) Michaelis-Menten kinetics (C) Competitive inhibition 2. The kinetic effect of purely competitive inhibitor of an enzyme: (A) Increases K without affecting Vma (B) Decreases K, without affecting Vmas (C) Increases Vma without affecting K (D) Decreases Vmas without affecting Km 3. In reversible non-competitive enzyme activity inhibition: (A) Vma is increased (C) Vma, is decreased (B) Co-operative binding (D) Non-competitive inhibition (B) K is increased (D) Concentration of active enzyme is reduced

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter6: Energy, Enzymes, And Biological Reactions

Section: Chapter Questions

Problem 9TYK: Which of the following statements about inhibition is true? a. Allosteric inhibitors and allosteric...

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1) Is the ratio of the forward rate constant and reverse rate constant changed by the presence of an enzyme catalyst? 2) 4) What is the simplest mathematical relationship between substrate concentrations [S], initial velocity (Vo) of an enzyme catalyzed reaction, the maximal velocity of the reaction (Vmax), and the ½ maximal Vo (i.e. Km) ? (Hint: what is the Michaelis-Menten Equation? 3) Graphically illustrate the most useful derivation of the Michaelis-Menton equation (that darn linearized, double-reciprocal)
5. For a Michaelis-Menten enzyme, k1 = 5.2 ⅹ 108 M-1 s-1, k-1 = 3.1 ⅹ 104 s-1, and k2 = 3.4 ⅹ 105 s-1. a) Write out the reaction, showing k1, k-1, and k2. Calculate Ks and Km. Does substrate binding approach equilibrium or the steady state? Justify your answer. b) What is kcat for this reaction? Justify your answer. c) Calculate Vmax for the enzyme. The total enzyme concentration is 25 pmol L-1, and each enzyme has two active sites. d) What substrate concentration would be required for the reaction in (c) to reach half of Vmax. Justify your answer mathematically. e) A second Michaelis-Menten enzyme has k1 = 4.2 ⅹ 107 M-1 s-1, k-1 = 6.1 ⅹ 104 s-1, and k2 = 5.3 ⅹ 102 s-1. Which enzyme is most efficient? 6. A pharmaceutical company is trying to develop a
1. Make a Lineweaver-Burk plot and use the plot to complete the information in the table and the following questions. a. Is it possible for the enzyme to overcome the effect of the inhibitor in question from the chart. Explain. b. What prevents this enzyme from being an even more catalytically efficient enzyme? c. What do single molecule data indicate about the validity of ensemble data?d. What is the reason that humans are insensitive to sulfa drugs?
An enzyme is found that catalyzes the reaction X ⇌ Y. Researchers find that the Km for the substrate X is 4 μM, and the kcat is 20 min−1.(a) In an experiment, [X] = 6 mM, and V0 = 480 nM min−1. What was the [Et] used in the experiment?(b) In another experiment, [Et] = 0.5 μM, and the measured V0 = 5 μM min−1. What was the [X] used in the experiment?(c) The compound Z is found to be a very strong competitive inhibitor of the enzyme, with an α of 10. In an experiment with the same [Et] as in (a), but a different [X], an amount of Z is added that reduces V0 to 240 nM min−1. What is the [X] in this experiment?(d) Based on the kinetic parameters given above, has this enzyme evolved to achieve catalytic perfection? Explain your answer briefly, using the kinetic parameter(s) that define catalytic perfection.
Which of the following statements about inhibition is true? a. Allosteric inhibitors and allosteric activators are competitive for a given enzyme. b. If an inhibitor binds the active site, it is considered noncompetitive. c. If an inhibitor binds to a site other than the active site, this competitive inhibition. d. A noncompetitive inhibitor is believed to change the shape of the enzyme, making its active site inoperable. e. Competitive inhibition is usually not reversible.
5.5 Explain the effect of each type of inhibitor on the apparent kinetic parameters: (1) Inhibitor binds only free enzyme does Km increase, decrease, not change? does Vmax increase, decrease, not change? (2) Inhibitor binds only ES complex does Km increase, decrease, not change? does Vmax increase, decrease, not change? (3)Inhibitor binds E and ES equally does Km increase, decrease, not change? does Vmax increase, decrease, not change?
4. a. Use the data in the graph above to estimate a KM value for the enzyme in the presence of these metabolites, and enter them into the table below. b. Classify these metabolites as either activators or inhibitors, and explain your rationale below.
A hypothetical enzyme that follows Michaelis-Menten kinetics functions has a substrate concentration 50mM at 50% of Vmax. Find the substrate concentration when the velocity of reaction is equal to 75% of Vmax.
Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-Menten kinetics is false? a. As [S] increases, the initial velocity of reaction V0 also increases. b. At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km. c. Km is the [S] at which V0 = 1/2 Vmax. d. The shape of the curve is a hyperbola. e. The y-axis is a rate term with units of μm/min.
One of the hallmarks of competitive inhibition is that there is constant competition betweenthe substrate and the inhibitor for binding to the enzyme active site.a) If [inhibitor] >> [substrate], which compound “wins” (i.e., occupies the active site a greaterpercentage of the time)?b) If [substrate] >> [inhibitor], which compound “wins” (i.e., occupies the active site a greaterpercentage of the time)?
Drug D reversibly binds to enzyme E and inhibits its activity toward substrate S. D binds equally well whether or not S is bound. Sketch a graph of the expected 1/v vs. 1/[S] relationship for: A) The enzyme reacting with S in the absence of drug D, B) The enzyme reacting with S in the presence of a small amount of drug D, and C) The enzyme reacting with S in the presence of a large amount of drug D.
Use the relationships revealed by a Lineweaver–Burk plot and the table of enzyme performance to calculate the ?max and ?M of the enzyme with no inhibitor, with inhibitor A, and with inhibitor B. Substrate concentration, [S], has units of micromolar, μM. Enzyme velocity, ?0, has units of micromole per minute, (μmol/min). Using data from only the extremes of the [S] range is unreliable. Select the type of inhibition displayed by inhibitor A. competitive noncompetitive uncompetitive Select the type of inhibition displayed by inhibitor B. competitive noncompetitive uncompetitive