Maximum rate of sites generating superoxide/hydrogen peroxide in isolated skeletal muscle mitochondria from wild‐type and tazkd mice at 3, 8, and 12 months of age. The rate of superoxide/hydrogen peroxide generated by sites associated with the NADH/NAD+(A‐E) and QH2/Q (G‐H) isopotential pools. In the NADH/NAD+isopotential pool, the rate of superoxide/H2O2production was measured from the flavin (F) binding sites of: (A) complex I (site IF), (B) site AF, (C) site BF, (D) pyruvate dehydrogenase (site PF), and (E) 2‐oxoglutarate dehydrogenase (site OF). Complex I produces superoxide/H2O2from two sites: (A) site IFand (F) site IQ(ubiquinone (Q) binding site). In sites associated with the QH2/Q isopotential pool, the rate of superoxide/hydrogen peroxide production was measured from (G) site EF, in the electron transfer flavoprotein (ETF) and ETF:ubiquinone oxidoreductase (ETF:QOR) system, (H) site DQ, in dihydroorotate dehydrogenase, (I) site GQ(glycerol 3‐phosphate dehydrogenase), (J) site IIF, in complex II, and (K) site IIIQo, in complex III. Values are mean ± SEM, n ≧ 3 independent mitochondrial preparations and were normalized by mitochondrial protein (ptn). *P < 0.001, 2‐way ANOVA.