The exposure of mitochondrial suspension to a broad spectrum ultraviolet light produced a lipoperoxide which was directly proportional radiant energy. The oxygen consumption of state 4 in mitochondrial respiration increased gradually, the ADP/O ratio and respiratory control ratio were decreased with an increasing dose of radiant energy. These photobiochemical changes in mitochondria were produced by ultraviolet light in the range of 260-300 nm in wavelength.
