What is the name of the process by which nitrogen gas is converted into ammonia or ammonium by bacteria and lightning?
The correct answer and explanation is:
Correct Answer: Nitrogen fixation
Explanation (300 words):
Nitrogen fixation is the process by which nitrogen gas (N₂) from the atmosphere is converted into a usable form like ammonia (NH₃) or ammonium ions (NH₄⁺). This process is crucial because most organisms cannot use atmospheric nitrogen directly, even though nitrogen makes up about 78% of Earth’s atmosphere.
There are two primary natural methods for nitrogen fixation:
- Biological Nitrogen Fixation (by bacteria):
Specialized bacteria, such as Rhizobium, Azotobacter, and cyanobacteria, can fix atmospheric nitrogen. Rhizobium lives in symbiotic relationships with the roots of leguminous plants (like beans, peas, and clover). These bacteria use an enzyme called nitrogenase to convert nitrogen gas into ammonia: N2+8H++8e−→2NH3+H2N_2 + 8H^+ + 8e^- \rightarrow 2NH_3 + H_2 The ammonia is then often quickly converted into ammonium ions in the soil, which plants can absorb and use to make proteins and nucleic acids. - Abiotic Nitrogen Fixation (by lightning):
During thunderstorms, lightning provides enough energy to break the strong triple bonds of nitrogen molecules. The free nitrogen atoms then react with oxygen to form nitrogen oxides (NO and NO₂). These oxides dissolve in rain and form nitrates (NO₃⁻) that are carried into the soil, where they can be absorbed by plants.
In addition to natural processes, industrial nitrogen fixation also occurs via the Haber-Bosch process, where atmospheric nitrogen is converted into ammonia under high temperature and pressure for fertilizer production.
Overall, nitrogen fixation is essential for maintaining the nitrogen cycle and supporting all forms of life by enabling nitrogen to enter the food chain. Without this process, ecosystems would lack the nitrogen compounds needed to build vital biomolecules.