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b) The straight portion of the graph for substrate concentration over time is indicative of a zero-order dependence on substrate for most of the reaction, but the curve at low [A] is indicative of a change to (in this case) a first-order dependence on [A].
The second assumption is that the total enzyme concentration does not change over time, thus [] = [] + [] =!. The Michaelis constant K M is experimentally defined as the concentration at which the rate of the enzyme reaction is half V max , which can be verified by substituting [S] = K M into the Michaelis–Menten equation and can also be seen ...
Therefore, it is valid to apply the steady state approximation only if the second reaction is much faster than the first (k 2 /k 1 > 10 is a common criterion), because that means that the intermediate forms slowly and reacts readily so its concentration stays low. The graphs show concentrations of A (red), B (green) and C (blue) in two cases ...
When studying urease at about the same time as Michaelis and Menten were studying invertase, Donald Van Slyke and G. E. Cullen [29] made essentially the opposite assumption, treating the first step not as an equilibrium but as an irreversible second-order reaction with rate constant +. As their approach is never used today it is sufficient to ...
The second step with OH − is much faster, so the overall rate is independent of the concentration of OH −. In contrast, the alkaline hydrolysis of methyl bromide (CH 3 Br) is a bimolecular nucleophilic substitution (S N 2) reaction in a single bimolecular step. Its rate law is second-order: r = k[R−Br][OH −].
The slope of a graph of ... is the initial concentration at zero time. The first-order rate law is ... the reaction can change from second order to first order as ...
The exponential function in parentheses corresponds to the fraction of total change that has been achieved as time passes and the difference between C ss and C 0 equals the total amount of change. Finally, at steady state, the concentration is expected to equal the rate of synthesis, production or infusion divided by the first-order elimination ...
Iron rusting has a low reaction rate. This process is slow. Wood combustion has a high reaction rate. This process is fast. The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. [1]