Nitrogen cycle

Nitrogen Cycle

The Nitrogen Cycle (pronunciation: /ˈnaɪtrədʒən ˈsaɪkəl/) is a biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among the atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes.

Etymology

The term "Nitrogen Cycle" is derived from the element Nitrogen, which is a chemical element with the symbol N and atomic number 7, and the word "Cycle", which refers to a series of events that are regularly repeated in the same order.

Process

The Nitrogen Cycle involves several steps which transform nitrogen from one form to another. It is a complex process that involves many different types of organisms. The main steps in the nitrogen cycle are:

1. Nitrogen Fixation: This is the process by which atmospheric nitrogen is converted into a form that plants can use. This is primarily carried out by certain bacteria and archaea.

2. Nitrification: This is the process by which ammonia is converted into nitrites (NO2-) and then into nitrates (NO3-). This is carried out by nitrifying bacteria.

3. Assimilation: This is the process by which plants absorb nitrates from the soil into their roots. Then the nitrates are converted into nitrogen-containing organic molecules, such as amino acids and DNA.

4. Ammonification: This is the process by which the organic nitrogen in dead organisms and waste products is converted into ammonia by decomposers.

5. Denitrification: This is the process by which nitrates in the soil are converted into gaseous nitrogen and returned to the atmosphere. This is carried out by denitrifying bacteria.

Related Terms

• Biogeochemical cycle
• Ecosystem
• Bacteria
• Archaea
• Ammonia
• Nitrite
• Nitrate
• Decomposer

External links

• Medical encyclopedia article on Nitrogen cycle
• Wikipedia's article - Nitrogen cycle

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