FCCP is a chemical uncoupler of electron transport and oxidative phosphorylation.

FCCP permeabilizes the inner mitochondrial membrane to protons, destroying the proton gradient and, in doing so, uncouples the electron transport system from the oxidative phosphorylation system. In this situation, electrons continue to pass through the electron transport system and reduce oxygen to water, but ATP is not synthesized in the process. FCCP acts similar to 2,4-dinitrophenol (DNP) in uncoupling electron transport and oxidative phosphorylation.