cycle of nitrogen



We explain what the nitrogen cycle is, what its stages are and its importance. Also, the nitrogen cycle in water.

The nitrogen cycle involves all living things, the soil and the atmosphere.

What is the nitrogen cycle?

The nitrogen cycle is the biogeochemical circuit that supplies nitrogen to the living beings and keeps it circulating in the biosphere. Nitrogen that forms part of the atmosphere in the form of N2 cannot be used by animals and the plants and for this reason a mechanism is needed to convert N2 to usable forms. This mechanism is responsible for some bacteria. Thus, the nitrogen cycle is composed of processes Biotics Y abiotic. The ammonium ion (NH4 +) and the nitrate ion (NO3–) form some of the most important presentations (usable by animals and plants) of this element in the cycle, as well as diatomic nitrogen in gaseous state (N2).

It's one of the biogeochemical cycles most important for the balance of life since nitrogen (N) is a chemical element extremely abundant in the composition of the organic material and in the Earth's atmosphere (78% of its volume).

In this cycle the different levels of living beings are interrelated, autotrophs Y heterotrophs, the tiny decomposing organisms of organic matter, and the immense volume of nitrogen in the atmosphere.

The nitrogen cycle can be summarized as follows:

  • Nitrogen fixation. Atmospheric nitrogen is converted into nitrogen oxides by the action of lightning, which helps its incorporation into the soils. On the other hand, this gaseous element is fixed by bacteria and other prokaryotes through processes metabolic diverse, which turn it into different usable compounds, such as ammonia (NH3) and ammonium ion (NH4 +). These microorganisms can be found in the ground and the Water, or as symbiotes of the plants. Said molecules Nitrogenous are used by plants, which make up various organic molecules with them.
  • Transmission to animals. Following the order of the food chain, the nitrogen in the plants passes to the herbivorous animals and then to carnivores, spreading among the different links of the food pyramid. Excess nitrogen is expelled from their bodies through urine, rich in ammonia, thus returning to the soil to continue the cycle.
  • Nitrification. Soil ammonia from animal urine or from the action of fixing bacteria serves as food for other types of nitrifying microorganisms, that is, they decompose ammonia and oxidize it to nitrites (NO2–), and then nitrites are oxidized to nitrates (NO3–).
  • Denitrifying decomposition. These compounds, in turn, serve as food for other types of prokaryotes, this time denitrifying metabolism, that is, they decompose nitrite and nitrate ions, and obtain Energy to live and releasing nitrogen back into the atmosphere in a gaseous state, so that the cycle can restart.

Importance of the nitrogen cycle

The nitrogen cycle is a vital circuit for the existence of life as we know it, since life forms such as animals, plants and even the human being we are unable to fix nitrogen from its gaseous form (N2), even though we need it enormously to produce amino acids, protein, nucleic acids Y DNA.

For this reason, we depend on the manipulation of gas by other forms of life, which are not less important because they are not microscopic. This is how nitrogen reaches us through a long chain of transmission.

Nitrogen cycle in water

The nitrogen cycle does not vary much when it occurs in water, that is, on the surface of lakes, seas and rivers. Nitrogen can get into water by runoff, as a result of its use in human-made or natural fertilizers. In other cases, it is transmitted by marine trophic chains, in which many aquatic and terrestrial animals intervene (in the case of feeding on aquatic animals).

In any case, this influx of nitrogenous organic substances is distributed among the different predators, leaving a residue of nitrogenous matter on the ocean floor, where it is decomposed by various types of microorganisms. Thus, the microscopic cycle between nitrifying and denitrifying is repeated and the nitrogen gas is released back into the atmosphere.

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