AI Tutor
If someone accidentally swallows toxic methanol, emergency room doctors administer an intravenous drip of ordinary ethanol. How can alcohol serve as an antidote to a deadly poison?
Ethanol physically blocks the enzyme alcohol dehydrogenase, buying the body time before toxic formaldehyde forms. This is enzyme inhibition in action.
How do biochemists mathematically determine which type of inhibitor is at work inside a cell?

The Double-Reciprocal Baseline

In 1934, American chemists Hans Lineweaver and Dean Burk inverted the hyperbolic Michaelis-Menten equation to yield a straight line: 1V0=(KmVmax⁡)1[S]+1Vmax⁡\frac{1}{V_0} = \left(\frac{K_m}{V_{\max}}\right)\frac{1}{[S]} + \frac{1}{V_{\max}}
A Lineweaver-Burk plot graphs 1/V01/V_0 on the y-axis against 1/[S]1/[S] on the x-axis. The y-intercept represents 1/Vmax⁡1/V_{\max}, the x-intercept represents −1/Km-1/K_m, and the slope equals Km/Vmax⁡K_m/V_{\max}.
What happens when an inhibitor molecule directly mimics the substrate and fights for the exact same active site?

Competitive Inhibition

In competitive inhibition, the inhibitor closely matches the substrate's shape and binds directly to the enzyme's active site.
Because high substrate concentrations can outcompete the inhibitor, Vmax⁡V_{\max} stays unchanged, but the enzyme requires more substrate to reach half-maximal speed, increasing the apparent KmK_m.
What if an inhibitor ignores the active site entirely and binds somewhere else on the protein?