How the biological clock works

Probably everyone heard about the biological clock. But how does the biological clock work, and what "gears" bring them into action? These questions cause an unceasing debate in the academic world. And it all began with Jean-Jacques de Maran, who in 1729 drew attention to the behavior of the heliotrope standing on the window in his office. Turning the leaves after the daylight, and sunset wilting leaves, this plant seems to fall asleep until the next morning. But the most interesting was that the heliotrope fell asleep and woke up at a strictly certain time, even in the dark.

Probably everyone heard about the biological clock. But how does the biological clock work, and what gears bring them into action?

Thirty years later Henry-Louis Duhamel confirmed the discovery of de Maran and continued his experiments, taking a few plants of this species. Placing the heliotrope in various dark rooms and conducting a lot of experiments, he wrote with a clear conscience: "Experiments allow us to conclude that the movement of leaves in plants does not depend on either light or heat." Like de Maran, Duhamel could not answer the question of how the biological clock of the heliotrope works.

Today it is known that these hours are started by changing day and night, daily fluctuations in temperature and pressure, changing the magnetic field and some other factors.

On the question of how the biological clock works, the American biologist Charles Eret tried to answer. Experimenting with the infusoria shoe, he, working on the DNA molecule, tried to break the rhythm of her life. A light beam was chosen as the instrument of influence. After a series of experiments he managed to find out that by acting on the shoe alternately with ultraviolet radiation and white light, one can greatly change the rhythm of the life of the ciliates, then restore it again. In this case, the ultraviolet damages the DNA helix, but the cell can repair the damage if it is exposed to white light after an ultraviolet pulse.

It could be considered proven that as a biological clock, living cells use DNA molecules. But how exactly does a biological clock work for a DNA molecule?

The DNA molecule is coiled in the nucleus of the cell with a tight helix. Erett claimed that when the duplication of a molecule begins, the filaments of such a spiral diverge, they construct an information RNA reaching the total length of a single strand of DNA. At the same time, a number of interrelated chemical reactions occur, the ratio of the rates of which can be regarded as the work of a clock regulating mechanism. But what kind of chemical reactions occur when DNA is duplicated - this issue remained open.

The key to unraveling the work of biological clocks may be the discovery by V.P. Belousov and M.Zhabotinsky of pulsating redox reactions in which the liquid in the test tube changed in color right before the eyes: just that it was red, here it is already blue, then reddened again... The discoloration was strictly periodic. The initial components of the pulsating reactions are organic substances, very similar in composition to the substances of the living cell, with the substances of DNA.

If you illuminate the tube in which such a reaction takes place, with monochromatic light of a certain wavelength, the brightness of the tube will change according to the sinusoidal law. In the end, it turns out that the reactions of Belousov-Zhabotinsky are something like a kind of chemical clock. So are not the pulsating reactions the answer to the question of how the biological clock works? But exactly how the chain of biochemical processes proceeds in all their completeness and complexity is yet to be understood.

Tools