Chem 132 Chapter 7 Quiz – Flashcards
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Which of the following is true about enzymes?
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enzyme activities can often be regulated
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A plot of velocity versus substrate concentration for a simple enzyme-catalyzed reaction produces a _____. This indicates that at some point, the enzyme is _____.
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hyperbolic curve; saturated with substrate
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When a substrate and enzyme interact, the first chemical species formed is _____.
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enzyme-substrate complex
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How is an enzyme-catalyzed reaction affected by the addition of more enzyme?
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velocity will increase
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Which of the following properly expresses the Michaelis-Menten equation?
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vo = Vmax [S] / (KM + [S])
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If an enzyme-catalyzed reaction has a velocity of 2 mM/min and a Vmax of 10 mM/min when the substrate concentration is 0.5 mM, what is the KM?
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2 mM
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If an enzyme-catalyzed reaction with a KM of 3.5 mM has a velocity of 5 mM/min at a substrate concentration of 0.5 mM, what is the Vmax?
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40 mM/min
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What is the kcat for a reaction in which Vmax is 0.4 mmoles/min and the reaction mixture contains 5 x 10-6 micromoles of enzyme?
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8 x 10^7 min-1
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The catalytic constant, or kcat, is also known as the _____.
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turnover number
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An extremely efficient enzyme has a _____ KM and a _____ kcat.
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small; large
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A Lineweaver-Burk plot is a _____.
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double reciprocal plot
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If a Lineweaver-Burk plot gave a line with an equation of y = 0.490 x + 0.059, what is the velocity at a substrate concentration of 5 mM? The original units for substrate were in mM and velocity in mM/s.
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6.37 mM/s
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If a Lineweaver-Burk plot gave a line with an equation of y = 0.25 x + 0.34, what are the values of KM and Vmax if the substrate concentration is in mM and the velocity in mM/s?
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0.74 mM and 2.9 mM/s
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Some irreversible inhibitors are called _____ because they bind to the active site of the enzyme and begin the catalytic process, just like a normal substrate.
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suicide substrates
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An inhibitor that binds to the active site only in the absence of the substrate and in a reversible fashion is a(n) _____.
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competitive inhibitor
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How are the kinetics of an enzyme-catalyzed reaction affected by a competitive inhibitor?
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Vmax unchanged, KM increased
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Which of the following is true regarding transition state analogs?
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all of the above:
they are competitive inhibitors
they bind to an active site with much higher affinity than most inhibitors
they are much more stable than the transition state
their affinity for an enzyme is often much greater that the substrate
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A reversible inhibitor that binds to a site other than the active site regardless of whether or not the substrate is bound is a _____.
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noncompetitive inhibitor
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How are the kinetics of an enzyme-catalyzed reaction affected by a purely noncompetitive inhibitor?
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Vmax decreased, KM unchanged
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If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction, both with and without a noncompetitive inhibitor present, what difference would be seen?
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the y-intercept would be higher with larger slope for the inhibited reaction
