Oxygen is the most important component of the existence of all life on Earth. Surprisingly, this element on our planet, although its concentration in the air, according to some scientists is inexorably decreasing, is a replenished reserve. Even more striking is the fact that it is synthesized from more than available resources - water, sunlight, and carbon dioxide. And they carry out this wonderful process of the plant.
Of course, we are talking about photosynthesis - an amazing creation of nature. Despite the fact that scientists thoroughly studied this issue, to repeat the steps of photosynthesis in laboratory conditions is unrealistic to this day.
This process is usually divided into two stages:
- Light phase of photosynthesis.
- The dark phase of photosynthesis.
From their name it is quite clear that the first part of the process takes place in the light, that is, with the participation of sunlight. It occurs only in the green leaves of plants, since they contain chloroplasts - special elements in the membranes of which ATP is synthesized - a molecule in which energy is stored.
When photons of sunlight enter the leaves of plants containing chlorophyll, the energy of sunlight converts into the energy molecules of ATP, already mentioned above. In addition, due to the cleavage of two hydrogen atoms from a water molecule (which also occurs with the help of sunlight), a NADP molecule is formed. A decomposed water molecule, devoid of two hydrogen atoms, remains with free oxygen, which enters the atmosphere. Thus, the products of photosynthesis in the light phase are:
- oxygen;
- ATP energy molecule;
- atomic hydrogen NADPH2.
Curiously, the formation of oxygen in this process is not at all the ultimate goal. Rather, it is a side effect. Next, the dark phase of photosynthesis, or chemosynthesis, takes place, in which the products of the first phase are directly involved. Let's consider it in more detail.
Indeed, the purpose of the process is not the formation of oxygen. The dark phase of photosynthesis proceeds in another part of the leaf — in the stroma of its chloroplasts. At the end of the light phase, the plant manages to stock up with an impressive amount of energy molecules - ATP and NADPH2, therefore, the participation of light is no longer necessary. It is with the help of these molecules that the synthesis of organic elements occurs. It is logical that the task of the ATP energy molecule is to supply energy for the implementation of synthesis processes, while the role of NADPH2 is restoration.
At the beginning of this phase, the reducing agent molecule is oxidized, due to which two hydrogen atoms disappear, which gives a pure NADP molecule at the output. At the same time, ATP gives up the remainder of phosphoric acid, turning into ADP. These two processes occur in the matrix of the sheet. The newly obtained molecules then return to the edges of the leaves, which makes it possible to repeat the entire process of the light phase. However, this is not a key process of photosynthesis, we only outlined the cyclical nature and sequence of operations occurring in the leaves.
The end product of this phase is glucose - an organic compound classified as simple sugars. For the first time, Melvin Calvin was able to describe in detail the synthesis of this molecule. It turned out that both molecules considered in the framework of the light phase, the energy and the reducing agent, are involved in the synthesis processes. In addition, 6 molecules of carbon dioxide (CO2), 24 hydrogen atoms, 6 water molecules are important elements for the formation of simple sugars:
6CO2 + 24H + ATP C6H12O6 + 6H2O.
The dark phase of photosynthesis is important for plants because, in addition to glucose, various amino acids, nucleotides, fatty acids and glycerin are formed during this period.
Photosynthesis is a highly unique natural process. It is not only the key to maintaining a constant level of oxygen in the atmosphere and the ozone layer, but also represents the perfection of nature, when organic are created from inorganic elements.