Question

2. We can measure how fast the Product is formed at increasing levels of Substrate Concentration The rate of the reaction can be plotted below. This is called a Michaelis-Menten Graph and it shows several important features of the enzyme: a. What happens to the reaction rate as the amount of substrate is increased? reaction rate- b. Why does the graph level off at high levels of substrate concentration? substrate concentration

Answer 1

A. The reaction rate increases linearly with increase in substrate concentration, until the reaction rate reaches a maximum and remains the same even after further increase in substrate concentration ( plateau phase of the graph).

B. During the enzyme catalyzed reaction, the enzyme E and substrate S form enzyme -substrate complex (ES). The latter (ES complex) then breaks down in to Enzyme E and the product P. During the linear phase of the reaction the enzyme molecules are free and increase in substrate will result in formation of more and more ES complex and thus more product. Hence the rate of the reaction increases with substrate concentration during this phase. When all the enzyme molecules are bound by the substrate forming ES complex the reaction rate reaches maximum value. Further increase in substrate concentration will not increase the reaction rate since there is no free enzyme to form complex with the substrate. This result in leveling off of the graph at higher substrate concentration.