Fig. 5

SDH complex (simplified). The flavin cofactor (FAD) is found in the catalytic subunit SDH subunit A, which takes electrons from succinate and transmits them to the Fe–S center in the SDH subunit B subunit. The electrons are subsequently transported through the SDHC and SDHD subunits' embedded ubiquinone pool. Within the mitochondrial inner membrane space, reduced Q (QH2 = ubiquinol) delivers electrons to complex III