UBIQUINONE
ubiquinone: translation
(= coenzyme Q)
Small molecule with a hydrocarbon chain (usually of several isoprene units) that serves as an important electron carrier in the respiratory chain. The acquisition of an electron and a proton by ubiquinone produces ubisemiquinone (a free radical) ; a second proton and electron convert this to dihydroubiquinone. Plastoquinone, which is almost identical to ubiquinone, is the plant form.