Nitrogen Fixation Nitrogen Metabolism

There are various elements present on our planet, such as oxygen, carbon, hydrogen, and other elements, which are essential for the survival of many living organisms. One of these elements is nitrogen. These can be found in a variety of nutrients such as vitamins, proteins, amino acids, and hormones. As a result, it is necessary to investigate these factors and their impacts as well. In accordance with NASA, the overall composition of air in the earth’s atmosphere is composed primarily of nitrogen gas, with 21% of the air being oxygen, 0.93 % of the air being argon, 0.04 % of the air being carbon dioxide, and minute amounts of other gasses. Numerous biological components are likewise composed primarily of nitrogen. However, even with all of this, the concentration of a usable form of nitrogen is quite low. Nitrogen gas is essential, yet it is also a constraining ingredient. Nitrogen is required by all species, including people, plants, and other animals, in order to carry out their everyday biological operations.

Nitrogen gas is in high demand due to a number of factors. The amount of useable nitrogen gas available for living things is significantly smaller despite the massive concentration of nitrogen gas. As a result, learning the definition of nitrogen fixation is crucial in order to gain an understanding of the various parts of the process.

Different Ways of Nitrogen Fixation

Plants are the primary source of nutrition. Plants synthesize the nutrients that they acquire from the soil and the atmosphere by utilizing a variety of elements that they obtain from both the atmosphere and the soil. The element nitrogen is included in this group of elements. Plants take up nitrogen from the soil and use it in the process of protein synthesis, which is essential for survival. Carbon dioxide and oxygen may be acquired from the atmosphere through the pores of leaves, but atmospheric nitrogen cannot. The reason for this is that plants are unable to utilize the nitrogen gas present in the atmosphere. Nitrogen fixation is aided by the presence of particular microbes and the occurrence of natural phenomena.

Biological Nitrogen Fixation

The conversion of atmospheric nitrogen to ammonia is possible due to the presence of certain bacteria or prokaryotes. Biological nitrogen-fixing is the term used to describe this process. Nitrogenase is a digestive enzyme that transforms dinitrogen to ammonia. Nitrogen-fixing bacteria can exist as free-living organisms or as part of a symbiotic relationship. Azotobacter, Beijernickia, Rhodospirillum, cyanobacteria, and other nitrogen-fixing bacteria are examples of free-living nitrogen fixers. Rhizobium (found in the root nodules of legumes) and Frankia (found in the root nodules of non-leguminous plants), among other organisms, are examples of symbiotic nitrogen fixers.

Symbiotic Nitrogen Fixation

Rhizobium bacteria, a type of bacteria that aids in nitrogen fixation, are present. They are bacteria that grow in the roots of leguminous plants (such as pea and bean plants) and, via the use of specific types of enzymes, they contribute to the fixation of nitrogen in the soil. During this biological process, they convert the non-absorbable nitrogen form into a usable form that may be used by the organism. This form of nitrogen dissolves in the soil, and the transformed nitrogen is absorbed by plants through the roots of the plants. Crop rotation, in which leguminous plants help to replace nitrogen levels in the soil without the need for fertilizers, is the reason why farmers practise crop rotation.

Nitrogen Fixation by Lightning

Lightning is yet another activity that contributes to nitrogen fixation. In this natural occurrence, the energy of lightning breaks apart and transforms the non-absorbable form of nitrogen into a usable form. Despite the fact that lightning has a little role in nitrogen fixation, it is nonetheless important because it prevents plants from becoming deficient in vital nutrients.

Nitrogen oxides, such as NO, N2O, and NO2, are also released into the atmosphere as a result of industrial activities, automotive exhaust, power plants, and forest fires, among other sources.

Nitrogen Metabolism

Metabolism is a collection of chemical reactions that are carried out in order to convert chemicals into forms of energy that can be used. In order to recycle ammonia (NH3) into the neutral or charged form of ammonium ion (NH4+), nitrogen metabolism must be carried out in a closed system. The Nitrogen Cycle is the most important component of nitrogen metabolism.

Nitrogen Cycle

The Nitrogen Cycle is the most important component of nitrogen metabolism. In order for a nitrogen molecule to be formed, two nitrogen atoms must be joined together by a very strong triple covalent bond (N N). There are three major sources of nitrogen in the environment: the atmosphere, soil, and biomass. It is possible to cycle nitrogen between these two pools in the following ways.

Atmospheric Pool

‘Nitrogen fixation is the term used to describe the process of turning atmospheric nitrogen (N2) into ammonia (NH3). The fixation of atmospheric nitrogen occurs in three ways: biologically, industrially, and electrically.

• It is possible to achieve “biological nitrogen fixation” by using living organisms that convert nitrogen to ammonia.

• The term “industrial nitrogen fixation” refers to the use of nitrogen from sources such as industrial combustion, automotive emissions, forest fires, and power-generating stations.

• When natural factors such as lightning and ultraviolet radiation supply enough energy to transform nitrogen into nitrogen oxides, this is referred to as “electrical nitrogen fixation.”

Soil Pool

The methods described above fix nitrogen from the atmosphere into the soil. As a result, nitrogen is taken up by plants and animals, and the cycle continues.

Biomass Pool

This process is known as ‘Ammonification,’ and it is responsible for returning nitrogen to the soil. Some of this ammonia evaporates and re-enters the atmosphere, but the majority of it is transformed into nitrate by soil bacteria, which occurs in the following ways:

i) First, the bacteria Nitrosomonas and/or Nitrococcus oxidise ammonia to nitrite, which is then oxidised further to nitrate.

2NH3 + 3O2 → 2NO2– + 2H+ + 2H2O

(ii) Nitrobacter then goes on to further oxidise nitrite, resulting in nitrate.

2NO2– + O2 → 2NO3–

These reactions are referred to as ‘Nitrification,’ and the bacteria that cause them are referred to as ‘Chemoautotrophs.’ Plants absorb the nitrate generated in this way and transfer it to the leaves, where it is converted to ammonia by photosynthesis. This ammonia is responsible for the formation of the amine group of amino acids. Pseudomonas and Thiobacillus are responsible for reducing nitrates in the soil to nitrogen during the process known as ‘Denitrification.’ 

Conclusion

In biology, nitrogen fixation is the process of converting free nitrogen gas from the atmosphere into nitrogen-containing molecules in the soil. These oxides dissolve in rainwater, generating dilute nitric acid as a result of the reaction. This nitric acid combines with the alkalis in the soil (such as limestone) and forms nitrates as a result of the reaction. Metabolism is a collection of chemical reactions that are carried out in order to convert chemicals into forms of energy that can be used.

Nitrogen metabolism is not only one of the most fundamental processes in plant physiology, but it is also one of the most significant components of the worldwide chemical cycle.