To investigate the physiological diversity in the regulation and control of mitochondrial oxidative phosphorylation, we determined the composition and functional features of the respiratory chain in muscle, heart, liver, kidney and brain. First, we observed important variations in mitochondrial content and intrastructure, on electron micrographs of the different tissue sections. The analysis of respiratory chain enzymes content by western blot also showed large differences between tissues, in good correlation with the expression level of mtTFA, and the activity of citrate synthase. On the isolated mitochondria, we observed a conserved molar ratio between the respiratory chain complexes, and a variable stoichiometry for coenzyme Q and cytochrome c, with typical values of [1-1.5]:[30-135]:[3]:[9-35]:[6.5-7.5] for CII:CoQ:CIII:cytc:CIV, in the different tissues. The functional analysis revealed important differences in respiratory chain complexes maximal velocities, with higher values in heart. However, calculation of the catalytic constants showed that brain contained the more active enzyme complexes. Hence, our study demonstrate that in tissues, oxidative phosphorylation capacity is highly variable and diverse, as determined by different combinations of (i) the mitochondrial content, (ii) the amount of respiratory chain complexes, and (iii) their intrinsic activity. In every tissues there was a large excess of enzyme capacities and intermediate substrates concentrations, as compared to what is required for state 3 respiration. To conclude we submitted our data to a principal component analysis that revealed three groups of tissues: muscle and heart; brain; liver and kidney.