What are the key processes in the nitrogen cycle?
Identify which compounds are involved in each process.
The key processes in the nitrogen cycle are:
1. Nitrogen fixation: This process converts atmospheric nitrogen gas (N2) into forms that plants and other living organisms can use. Nitrogen-fixing bacteria, such as Rhizobium in legume root nodules, convert N2 into ammonia (NH3), which is then further converted into ammonium (NH4+) in soil.
2. Nitrification: Nitrification is a two-step process. Firstly, ammonium (NH4+) is converted by nitrifying bacteria into nitrite (NO2-). Secondly, nitrite is further oxidized by other nitrifying bacteria into nitrate (NO3-), which is the main form of nitrogen used by plants.
3. Assimilation: In this process, plants and other microorganisms take up nitrate (NO3-) through their roots and convert it into organic compounds, such as amino acids and proteins, which are essential for growth and development.
4. Ammonification: This process involves the decomposition of organic matter, such as dead plants and animal waste, by bacteria and fungi. During ammonification, organic nitrogen compounds are broken down into ammonia (NH3) and ammonium (NH4+).
5. Denitrification: Denitrifying bacteria carry out this process, which converts nitrate (NO3-) back into atmospheric nitrogen gas (N2), completing the nitrogen cycle. Denitrification occurs in oxygen-depleted soil or water environments.
The compounds involved in each process are:
- Nitrogen fixation: N2, NH3, NH4+
- Nitrification: NH4+, NO2-, NO3-
- Assimilation: NO3-
- Ammonification: NH3, NH4+
- Denitrification: NO3-, N2