Why does an elephant live twenty times longer than a mouse? Partly just because it's bigger, but even after correcting for body mass, mammals with fast metabolic rates (high oxygen consumption), such as mice, age and die swiftly, whereas animals with slow metabolic rates, such as elephants, live longer and age more slowly.
ILLUSTRATION BY JOELLE BOLT
Mitochondria have different strategies for minimizing oxidative stress. (A) In the respiratory chain, reduced complexes (red) are generally more reactive than oxidized complexes (blue) and therefore generate more free radicals (
). (B) Polymorphisms in mtDNA can lead to low free-radical leakage despite strongly reduced complexes. (C) Uncoupling of the respiratory chain leads to fast electron flow and low leakage due to relatively oxidized complexes. (D) Larger surface area for mitochondrial membranes, with the same number of electrons entering overall, produces mainly...