Nitrogen fixation is the conversion of 
 

Both A and B

Nitrogen fixation involves converting atmospheric nitrogen into nitrates and ammonia through nitrogen-fixing bacteria.

Understanding Nitrogen Fixation

Nitrogen fixation is a crucial biological process in the nitrogen cycle that converts atmospheric nitrogen (N₂) into forms that are usable by plants and other organisms. Nitrogen, which makes up about 78% of Earth's atmosphere, is an inert molecule and cannot be directly utilized by plants or animals in its atmospheric form. Therefore, it needs to be transformed into compounds such as nitrates (NO₃⁻) and ammonia (NH₃), which can be absorbed by plants for growth.

Process of Nitrogen Fixation

1. Biological Nitrogen Fixation:
   • This process is primarily carried out by nitrogen-fixing bacteria such as Rhizobium (found in the root nodules of leguminous plants) and Azotobacter (found in soil). These bacteria have the ability to break the strong triple bond in atmospheric nitrogen molecules, converting N₂ into ammonia (NH₃).
   • The ammonia produced is then converted into ammonium (NH₄⁺) or other nitrogen compounds, which can be absorbed by plants.
2. Nitrification:
   • The process doesn't end at ammonia. Nitrogen-fixing bacteria convert ammonia into nitrates (NO₃⁻), which plants can easily absorb and use for synthesizing essential amino acids, proteins, and other vital organic compounds.
3. Importance of Nitrogen Fixation:
   • Nitrogen is a vital component of amino acids, proteins, and nucleic acids (DNA and RNA). Thus, nitrogen fixation is fundamental for the synthesis of these molecules, ensuring the survival and growth of living organisms. Without nitrogen fixation, the soil would lack accessible nitrogen, stalling plant growth and consequently affecting all life forms that depend on plants.