A researcher studying enzyme kinetics plots 1/v against 1/[S] (Lineweaver-Burk plot) for an enzyme with and without an inhibitor. The inhibitor increases both the x-intercept and y-intercept equally, and the lines cross on the y-axis. This pattern is characteristic of which type of inhibition?

• A Uncompetitive inhibition
• B Competitive inhibition ✓
• C Non-competitive (pure) inhibition
• D Mixed inhibition

Explanation

In competitive inhibition, the inhibitor increases apparent Km (shifts x-intercept toward zero, i.e., x-intercept becomes less negative, meaning -1/Km shifts) while Vmax remains unchanged (same y-intercept = 1/Vmax unchanged). The two lines intersect at the y-axis in the Lineweaver-Burk plot. Non-competitive inhibition increases the y-intercept (reduces Vmax) while Km is unchanged; lines intersect on the x-axis. Uncompetitive inhibition shifts both y-intercept and x-intercept by the same factor, giving parallel lines.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.