Multiple Choice
Which of the following rate constants is negligible for the initial velocity (V 0) of an enzyme-catalyzed reaction?
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6. Enzymes and Enzyme Kinetics
Rate Constants and Rate Law
Multiple Choice
In a typical enzyme-catalyzed reaction, when & why is the rate constant k -2 negligible?
A
At the very beginning of a reaction because the [S] & [P] are at equilibrium and not yet disturbed by the enzyme.
B
Initially towards the beginning of a reaction because enzymes are getting off to a slow start.
C
At the start of a reaction when [S] are at their highest, [P] are at their lowest, & the reverse reaction is unlikely.
D
At the end of a reaction when the substrate and product are at equilibrium with each other.
E
As soon as the reaction begins when the reaction rate is at its lowest.
Verified step by step guidance1
Understand the context of enzyme-catalyzed reactions: Enzymes accelerate reactions by lowering the activation energy, and the rate of reaction is influenced by substrate concentration [S] and product concentration [P].
Identify the role of rate constants: In enzyme kinetics, the rate constant k-2 refers to the reverse reaction rate constant, which is the rate at which the product converts back to the substrate.
Consider the conditions at the start of the reaction: At the beginning, the substrate concentration [S] is at its highest, and the product concentration [P] is at its lowest, making the reverse reaction (product to substrate) less likely.
Analyze why k-2 is negligible initially: Since the reverse reaction is unlikely due to low [P], the rate constant k-2 has minimal impact on the overall reaction rate at the start.
Conclude with the significance of k-2: As the reaction progresses and [P] increases, k-2 becomes more relevant, but initially, it is negligible because the forward reaction is favored due to high [S] and low [P].
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