To solve this problem we need to use the Michaelis-Menten equation.

where is reaction rate, is maximum reaction rate, is substrate concentration, and is the Michaelis constant. If we plug in the given values we get a reaction rate of

Note that the Michaelis-Menten equation implies that the will never exceed . Regardless of how high the substrate concentration is, the reaction rate will approach but will never equal or exceed it. You can try this by substituting very high values for substrate concentration. The will get very close to 0.2 () but will never equal or exceed it.

Michaelis constant, or , is defined as the concentration of substrate at which the reaction rate is half the maximum (). It is a useful measure of how much substrate is needed for reaction to proceed rapidly. A reaction with a high Michaelis constant will need lots of substrate to reach high reaction rates whereas a reaction with low Michaelis constant will need small amounts of substrate to reach high reaction rates.

Reaction rate, according to Michaelis-Menten model is as follows.

where is reaction rate, is maximum reaction rate, is substrate concentration, and is the Michaelis constant. If we analyze the given options, we will observe that the greatest increase in occurs when is doubled (increased by a factor of 2). Increasing substrate concentration by a factor of 2 will have nearly the same effect; however, since is also found in the denominator it will only slightly contribute to an increase in .

Note that the units for is molarity, is molarity, and is . Solving for will give us units of .

The Michaelis-Menten equation is as follows.

Where is reaction rate, is maximum reaction rate, is substrate concentration, and is the Michaelis constant. Since the Michaelis constant, , is in the denominator, the reaction rate is inversely proportional to the Michaelis constant; therefore, increasing the Michaelis constant will decrease the reaction rate.