There are several elements present on our earth like oxygen, carbon, hydrogen, etc. which are vital for many living organisms. Nitrogen is one of them. These are present in various vitamins, proteins, amino acids, and hormones. Consequently, these elements and their effects must be studied too. As per NASA, the atmospheric air comprises 78% nitrogen, 21% oxygen gas, 0.04% carbon, 0.93% argon, while the other gases are present in a small amount.
Notably, despite its colossal concentration, the amount of usable nitrogen gas available for living organisms is less. Therefore, it becomes essential to learn nitrogen fixation definition to get an idea about its various aspects.
The nitrogen present in the atmosphere is a di-Nitrogen molecule which is non-reactive. Resultantly, plants and other living organisms cannot use it. Therefore, conversion of non-usable form of nitrogen into usable form is necessary. This process is termed as nitrogen fixation. In this process, this molecular nitrogen is converted into usable forms or compounds like ammonia or other nitrogenous elements that are mixed in the soil.
To explain nitrogen fixation, it is one of the early stages in the nitrogen cycle, and the conversion takes place using bacterial species such as azotobacter, rhizobium, etc. or via natural phenomena.
Nitrogen fixation can be broadly categorised into two parts –
Physical Nitrogen Fixation – About 10% of nitrogen fixation is done by using physical methods. One such physical process is lightning wherein a di-Nitrogen molecule reacts with oxygen to form Nitric oxide. This is oxidised to form NO2 (Nitrogen Peroxide). Along with the rain, it forms nitrous and nitric acid, which gets mixed in the soil.
Biological Nitrogen Fixation – About 90% of nitrogen fixation examples are from biological processes. Here the conversion takes place with the help of a few living organisms.
One such process of biological nitrogen fixation mechanism (BNF) is when the molecular nitrogen is converted to ammonia in the presence of a biological catalyst known as nitrogenize. This compound is a naturally occurring catalyst and is found in microorganisms like frankia, symbiotic rhizobium, azotobacter, etc.
It is the process of converting molecular di-Nitrogen into ammonia in the presence of an enzyme named nitrogenase. The reaction can be written as follows.
N2 + 8 H+ + 8 e− → 2 NH3 + H2
It is a biological nitrogen fixation process. Further, look at the image shown below to understand the reaction.
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Metabolism refers to the process which is used for converting a compound or element into its usable form. For instance, ammonia is recycled to form charged particles such as ammonium ion or to its neutral form so that it can get mixed in the soil and becomes available for the plant to use it.
Conversion of nitrogen into nitrogenous elements or ammonia is termed as
Nitrogen fixation definition
Choose the applicable option about how plants absorb nitrogen molecule
All of the above
Choose the one which is not a free-living di-Nitrogen molecular fixer
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1. What do You Mean by Nitrogen Fixation?
Ans. To define nitrogen fixation, this is the process of converting molecular di-Nitrogen into its nitrogenous forms using various physical or biological methods. The conversion is critical so that more amount of Nitrogen is available for use.
2. What are Biological Nitrogen Fixers?
Ans. Utilisation of molecular Nitrogen present in the atmosphere is done by a few cyanobacteria and bacteria which are known as biological nitrogen fixers. Azotobacter, Rhizobium, Anabaena, Aulosira, etc. are a few examples of it.
3. What do you Understand by De-Nitrification?
Ans. It is the process wherein Nitrates are reduced back to their molecular or inert gas form. These are usually carried out in the presence of bacterial species like Pseudomonas and Clostridium.