The photobiology
Living beings are composed of organic materials, often complex, classified
as proteins, lipids and carbohydrates. Their molecular mass can reach high
values (sometimes up to 40 or 50 000 times less than that of the hydrogen atom).
It can also be very moderate, as in the case of certain carbohydrates. The
main character of organic substances is to be composed mainly of carbon, hydrogen,
oxygen and nitrogen. Other simple substances (calcium, phosphorus, potassium,
sodium, etc. ...) can be incorporated in these molecules. But, whatever their
complexity, their intimate constitution is the same as those of inert bodies.
In particular, they include processions of electrons that can be displaced
or ejected by photons of energy average or high. The purpose of this statement
does not list the mutilation, or. destruction that may suffer the living when
they were exposed to atomic radiation, consisting of photons and particles
of very high energy. But the sensitivity of human skin to a simple sunbathing,
the perception by the eye of colorful images, the use of light by chlorophyll
in plants are just banal aspects, and in fact already well known what is currently
known as "the photobiology". It is, in short, a simple extension
of the principles of classical photochemistry of complex organic molecules,
an essential constituent of all living beings in these molecules, the electrons
moved in orbits more distant nuclei, restore energy they receive when they
return to their original position. This is often the source of the photobiological
effect.
The study of this effect may occur at levels of accuracy very different. For
example, one can observe the action of the intensity of natural light on the
fixing of carbon dioxide and release oxygen through photosynthesis of various
plants, all other environmental conditions (temperature, water supply, air
concentrations of carbon dioxide, soil, etc ...) remain constant. relatively
simple instruments to measure the energy intensity of radiation, and devices
of a complexity not excessive to quantify the intensity photosynthesis are
then sufficient.
But we may want more precision, for example, determining the exact percentage of each of the radiation absorbed by the chlorophyll bodies, transfer of energy from the radiation of intermediates of short duration, the exact nature of these substances those formed in the light only, and those that can form in the dark, the actual energy performance of the reaction, etc. ... In this case we must use strictly monochromatic light sources, precision spectrophotometers, analytical methods such as special
chromatography, or electromagnetic processes
use very recently to obtain a more detailed analysis of phenomena.
But in all these cases, there is always
the photobiology, and the basic principles remain unchanged.
Thus, current theories on the intimate structure of molecules and atoms, and the nature of radiation, is a remarkably coherent whole. Probably they do not correspond exactly to the underlying reality of these highly complex phenomena (synthetic theory which can, moreover, boast of doing so?). But this set of concepts can be grasped in their broad outlines, it suggests new experiments, opens up attractive, and both in its logical construction as the practical results he has achieved, it appears worthy of great interest..