I know that sodium azide and 2,4-DNPH inhibit proton pumps. The azide is called an inhibitor and 2,4-DNP is called uncoupler. I want to know what's the difference between the mechanisms of action of sodium azide and 2,4-DNPH in proton pumps. Why is one called an inhibitor and the other an uncoupler?
There's a decent presentation here that basically goes over what you're asking.
As an inhibitor, azides are similar to cyanide in that they inhibit complex IV by binding cytochrome oxidase, resulting in a sort of chemical asphyxiation.
Uncouplers are a little harder to wrap your head around. They embed in the membrane space, and we know that ETC and proton pumping depends on the established proton gradient across a membrane. Uncouplers uncouple the proton gradient from the electron transport chain, allowing protons to diffuse across the membrane, effectively negating the proton gradient.