Question

If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction, both with and without an uncompetitive inhibitor present, what difference would be seen?

a) Parallel lines
b) Crossed lines
c) Converging lines
d) Diverging lines

Answer 1

In the Lineweaver-Burk plot, an uncompetitive inhibitor results in parallel lines because both Vmax and Km are lowered equally, keeping the slope constant while shifting the y-intercept.

Step-by-step explanation:

If a Lineweaver-Burk plot was made for an enzyme-catalyzed reaction both with and without an uncompetitive inhibitor present, the difference that would be seen is parallel lines.

Lineweaver-Burk plots are double reciprocal plots where the x-axis represents 1/[S] (the reciprocal of substrate concentration) and the y-axis represents 1/v (the reciprocal of reaction velocity). An uncompetitive inhibitor binds only to the enzyme-substrate complex, which means it lowers both the apparent maximum velocity (Vmax) and the apparent Michaelis constant (Km) equally. This concurrent lowering of Vmax and Km results in lines that have the same slope (Km/Vmax) but different y-intercepts, since the maximum velocity is reduced in the presence of an uncompetitive inhibitor.

Thus, when comparing plots with and without uncompetitive inhibition, the Lineweaver-Burk plots will show parallel lines.