Question

6. Calcute the substrate concentration required for to obey Michaelis - Menten Kinetics to reach 2/3 of its Vmax.
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Answer 1

Explanation:

The Michaelis-Menten Model Accounts for the Kinetic Properties of Many Enzymes

The primary function of enzymes is to enhance rates of reactions so that they are compatible with the needs of the organism. To understand how enzymes function, we need a kinetic description of their activity. For many enzymes, the rate of catalysis V0, which is defined as the number of moles of product formed per second, varies with the substrate concentration [S] in a manner shown in Figure 8.11. The rate of catalysis rises linearly as substrate concentration increases and then begins to level off and approach a maximum at higher substrate concentrations. Before we can accurately interpret this graph, we need to understand how it is generated. Consider an enzyme that catalyzes the S to P by the following pathway:

Image ch8e20.jpg

Figure 8.11. Michaelis-Menten Kinetics.

Figure 8.11

Michaelis-Menten Kinetics. A plot of the reaction velocity (V0) as a function of the substrate concentration [S] for an enzyme that obeys Michaelis-Menten kinetics shows that the maximal velocity (Vmax) is approached asymptotically. The Michaelis constant (more...)

The extent of product formation is determined as a function of time for a series of substrate concentrations (Figure 8.12). As expected, in each case, the amount of product formed increases with time, although eventually a time is reached when there is no net change in the concentration of S or P. The enzyme is still actively converting substrate into product and visa versa, but the reaction equilibrium has been attained. Figure 8.13A illustrates the changes in concentration observed in all of the reaction participants with time until equilibrium has been reached.