Stable circadian rhythms as a property of cell populations

Our paper analyzes the main difficulties which the theory of circadian rhythms encounters in an attempt to explain the mechanisms of biological clocks. It is shown that the assumption of a small concentration of the enzymes involved in the cell-clock mechanism allows explaining such well-known properties of biological clocks as: 1) a large period of the circadian oscillation; 2) insignificant energy consumption; 3) insensitivity to inhibitors; 4) temperature independence; 5) initiation of circadian oscillations in response to a short single external impulse; 6) a limited possibility of synchronization by periodic external factors. It is shown also that the self-oscillating clock mechanism may exist at the level of cell populations. This mechanism is considered to be a temperature-dependent component of the circadian clocks in multicellular organisms.