When substrates are present at relatively high concentration...

When substrates are present at relatively high concentration and are catalyzed by enzymes, the effect on reaction rate of changing substrate concentration can be described by zeroth-order kinetics. By what factor does the rate of an enzyme-catalyzed reaction change when the substrate concentration is changed from $1.5 \times 10^{-3}$ to $4.5 \times 10^{-2} \mathrm{M}$ ?

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Key Concepts

Enzyme Kinetics

This concept deals with the rates at which enzyme-catalyzed reactions occur. It involves the study of how different conditions, especially substrate concentration, affect the velocity of the reaction. Enzyme kinetics is often described by models such as the Michaelis-Menten equation, which quantifies the relationship between substrate concentration and reaction rate.

Michaelis-Menten Kinetics

This is a fundamental model in enzyme kinetics that explains how the reaction rate depends on substrate concentration. According to the Michaelis-Menten equation, as substrate concentration increases, the reaction rate increases until it reaches a maximum velocity, Vmax, where the enzyme becomes saturated with substrate. At this point, further increases in substrate concentration do not affect the reaction rate.

Zeroth-Order Kinetics

Zeroth-order kinetics refers to the situation where the reaction rate is independent of substrate concentration. This typically occurs when the enzyme active sites are fully saturated with substrate, meaning that every enzyme molecule is actively converting substrate to product at its maximum rate. Under these conditions, even significant changes in substrate concentration will not alter the reaction rate.

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