Abstract
The action on mitochondrial respiration of a ubiquinone analog, chloroquine, has been studied using purified mitochondria from the cotyledons of germinating peas (Pisum sativum L. var. Homesteader). Chloroquine at 3 millimolar did not inhibit malate or succinate oxidation at pH 7.2, but it did inhibit malate (but not succinate) oxidation at pH 8.2. Cyanide-resistant respiration was also inhibited.The implications of these experiments on the role of ubiquinone in the cyanide-resistant respiratory pathway and on the location of the alternate oxidase are discussed.