Biochemical, biophysical and functional properties of the genetic and membrane apparatus of the cell were considered activity and regulatory properties of the membrane and cytosolic enzymes of organs and tissues of mice exposed to radiation in the wide range of doses of 6 to 1800 mGy with the radiation intensity of 4.1 x 10(-3) and 41 x 10(-3) mGy/min. It was shown that the dose-dependence of changes in the investigated properties is of non-linear polymodal (bimodal) nature. The value of the maximum and the dose at which the latter was observed depend on the object's nature, radiation intensity and time passed after irradiation. An essential factor is that sensitivity of molecules, cells, organs and animals exposed to low-dose radiation to other damaging effects changes. The explanation is given in terms of the changes in the relation between the quantity of damages and the activity of reparation systems induced by low-dose irradiation.