Photosynthesis as a chemical phenomenon is a process during which the formation of organic compounds occurs during the interaction of water and carbon dioxide. An indispensable condition is the occurrence of the process in the light, with the direct participation of photosynthetic substances. For the plant world, such substances are chlorophyll, for bacteria - bacteriochlorophyll.
This reaction is inherently multi-stage and has a quantum character. Multistage is manifested in the fact that during photosynthesis, the processes of receiving, converting and using the received quantum energy of light proceed sequentially. One of these transformations is the process of transformation of carbon dioxide into organic matter. And the process during which energy-saturated molecules and ATP compounds appear is called the light phase of photosynthesis. The main condition and factor in the course of this phase is the presence of light energy. The mechanism for ensuring such a transformation as the light phase of photosynthesis can be schematically presented as follows. Chlorophyll, which is located on membranes in chloroplasts of plants, absorbs light fluxes of solar energy. This energy then promotes the combination of phosphoric acid elements with elements of ATP and ADP molecules. However, the work of light energy does not end there. In addition to influencing the process of fusion of molecules, this energy makes it possible to carry out the reaction of splitting of water elements. Here, the light phase of photosynthesis proceeds in the form of the reaction 2H20 = 4H + + 4e- + O2. As you can see, the result of this reaction is the released oxygen, which then in free form simply enters the natural environment.
The next stage, during which the light phase of photosynthesis is realized, is the activation of chlorophyll molecules. During this process, under the influence of light quanta, the electron of the chlorophyll molecule moves to a higher electronic level in the structure of the molecule. Catalysts and carriers of this electron are the elements of chloroplast proteins. Passing through a certain sequence of these carrier proteins, the electron of the chlorophyll molecule is forced to lose its energy, and it is spent on maintaining the oxidation-reduction process in ATP molecules.
Thus lost their energy and elements (electrons), chlorophyll molecules are restored due to the addition of electrons, which appeared as a result of the already mentioned reaction of the splitting of a water molecule. The hydrogen formed in the process of this cleavage is synthesized with another substance, which will be able to play the role of its transporter within the chloroplast.
Plants naturally exist in the dark, that is, when the flow of light energy is absent. Therefore, the dark stage of photosynthesis also occurs, which takes place in the space enclosed between the membrane and the thylakoids of the chloroplast. For this phase, light energy is not needed, and the reaction itself consists of the processes of successive transformation of carbon dioxide molecules entering their atmospheric air. The result of such transformations is the formation of glucose molecules, primarily, and other organic compounds. Such compounds are amino acids, nucleotides, as well as well-known glycerin.
In addition to the division into phases of photosynthesis, science considers the classification of this natural process by type. The main ones are C3 photosynthesis, and C4 photosynthesis, in which three- and four-carbon compounds are formed, respectively.