Fig. 3.

Electron transport chain and reverse electron transfer. a Membrane carrier ubiquinone accepts electrons from CI and SDH (QH₂) and transports them to CIII from where the electrons are carried by cytochrome c (cyt c) to CIV and reduce molecular oxygen to water. b Under conditions of high concentrations of succinate and high mitochondrial transmembrane potential (ΔΨ), the ubiquinone pool becomes over-reduced and transfers electrons to CI where they escape as ROS