In biochemistry, electron bifurcation (EB) refers to a system that enables an unfavorable (endergonic) transformation by coupling to a favorable (exergonic) transformation.
Two electrons are involved: one flows to an acceptor with a "higher reduction potential and the other with a lower reduction potential" than the donor.
[1] The process is suspected of being common in bioenergetics.
Quinones and flavins are cofactors that are capable of undergoing 2 e− – 2 proton redox.
[2] A pervasive example of electron bifurcation is the Q cycle, which is part of the machinery that results in oxidative phosphorylation.