The dark phase of photosynthesis

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 inexorably decreases, is a spare stock. 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 the scientists thoroughly studied this issue, it is impossible to repeat the stages of photosynthesis in the laboratory to this day.

This process is usually divided into two stages:

• The light phase of photosynthesis.
• The dark phase of photosynthesis.

From their name it is quite clear that the first part of the process proceeds in the light, that is, with the participation of the sun's rays. It occurs only in the green leaves of plants, because they contain chloroplasts - special elements, in the membranes of which the synthesis of ATP - a molecule in which energy is stored.

When sunlight photons hit the leaves of plants containing chlorophyll, the energy of sunlight is transformed into energy molecules of ATP, already mentioned above. In addition, due to the splitting off of two hydrogen atoms from the water molecule (which also happens with the help of sunlight), a NADP molecule is formed. The 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;
• Energy molecule of ATP;
• Atomic hydrogen NADP H2.

It is curious that the formation of oxygen in this process is not at all the ultimate goal. Rather, it is a side effect. Then comes the dark phase of photosynthesis, or chemosynthesis, in which the products of the first phase are directly involved. Let us 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 an impressive number of energy molecules - ATP and NADP H2, hence the participation of light is no longer necessary. It is with the help of these molecules is the synthesis of organic elements. It is logical that the task of the ATP energy molecule is the supply of energy for the synthesis processes, while the role of NADPH is the reduction.

At the beginning of this phase the reductant molecule is oxidized, due to which two hydrogen atoms disappear, which gives a pure NADPH molecule at the output. At the same time, ATP gives up the rest of phosphoric acid, turning into ADP. These two processes occur in the matrix of the sheet. The newly obtained molecules return to the leaf edges, which makes it possible to repeat the whole process of the light phase. However, this is not the key process of photosynthesis, we just indicated the cyclicity and sequence of operations occurring in the leaves.

The final product of this phase is glucose, an organic compound attributable to simple sugars. Melvin Calvin was the first to describe the synthesis of this molecule in detail. It was found out that both molecules, considered within the framework of the light phase, energy and reductant, participate 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 to plants because in addition to glucose during this period, various amino acids, nucleotides, fatty acids and glycerol are formed.

Photosynthesis is a highly unique natural process. It is not only a pledge to maintain a constant level of oxygen in the atmosphere and the ozone layer, but also is a perfection of nature when organic substances are created from inorganic elements.