nitrogen cycle

Biology

(noun)

the natural circulation of nitrogen, in which atmospheric nitrogen is converted to nitrogen oxides and deposited in the soil, where it is used by organisms or decomposed back to elemental nitrogen

Related Terms

  • nitrogen fixation
  • carbon cycle
Microbiology

(noun)

The natural circulation of nitrogen, in which atmospheric nitrogen is converted to nitrogen oxides by lightning and deposited in the soil by rain where it is assimilated by plants and either eaten by animals (and returned as feces) or decomposed back to elemental nitrogen by bacteria.

Examples of nitrogen cycle in the following topics:

  • The Nitrogen Cycle

    • The nitrogen cycle is the process by which nitrogen is converted from organic to inorganic forms; many steps are performed by microbes.
    • The nitrogen cycle describes the conversion of nitrogen between different chemical forms.
    • Nitrogen is essential for the formation of amino acids and nucleotides.
    • It can either be cycled back into a plant usable form through nitrification or returned to the atmosphere through de-nitrification.
    • Describe the nitrogen cycle and how it is affected by human activity
  • The Nitrogen Cycle

    • Nitrogen is cycled through the earth via the multi-step process of nitrogen fixation, which is carried out by bacteria.
    • Cyanobacteria are able to use inorganic sources of nitrogen to "fix" nitrogen.
    • The nitrogen that enters living systems by nitrogen fixation is successively converted from organic nitrogen back into nitrogen gas by bacteria .
    • A similar process occurs in the marine nitrogen cycle, where the ammonification, nitrification, and denitrification processes are performed by marine bacteria.
    • Although the movement of nitrogen from rock directly into living systems has been traditionally seen as insignificant compared with nitrogen fixed from the atmosphere, a recent study showed that this process may indeed be significant and should be included in any study of the global nitrogen cycle.
  • Nitrospirae and Deferribacter

    • Nitrospirae is a phylum of bacteria; some nitrospirae species perform important functions in the nitrogen cycle.
    • Some nitrospirae species perform important functions in the Nitrogen Cycle :
    • The Nitrogen Cycle describes the changes in nitrogenous compounds in the environment.
    • Because many of them are toxic, it is important to know something about this cycle.
    • Luckily, these compounds are converted to less and less toxic forms through this Nitrogen Cycle.
  • The Role of Prokaryotes in Ecosystems

    • Prokaryotes play vital roles in the movement of carbon dioxide and nitrogen in the carbon and nitrogen cycles.
    • Prokaryotes play many roles in the environments they occupy, but the roles they play in the carbon and nitrogen cycles are vital to life on earth.
    • Prokaryotes play an important role in the carbon cycle .
    • In this case, the cycle is based on one-carbon compounds.
    • As a macronutrient in nature, it is recycled from organic compounds to ammonia, ammonium ions, nitrate, nitrite, and nitrogen gas by myriad processes, many of which are carried out solely by prokaryotes; they are key to the nitrogen cycle .
  • Nitrogen Fixation: Root and Bacteria Interactions

    • Atmospheric nitrogen, which is the diatomic molecule N2, or dinitrogen, is the largest pool of nitrogen in terrestrial ecosystems.
    • However, nitrogen can be "fixed."
    • Through symbiotic nitrogen fixation, the plant benefits from using an endless source of nitrogen from the atmosphere.
    • Schematic representation of the nitrogen cycle.
    • Abiotic nitrogen fixation has been omitted.
  • Nitrogenase and Nitrogen Fixation

    • Nitrogen fixation also refers to other biological conversions of nitrogen, such as its conversion to nitrogen dioxide.
    • Nitrogen fixation is a process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3).
    • Atmospheric nitrogen or elemental nitrogen (N2) is relatively inert: it does not easily react with other chemicals to form new compounds.
    • Microorganisms that fix nitrogen are bacteria called diazotrophs.
    • Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called nitrogenase.
  • Sources and Sinks of Essential Elements

    • Most important substances on Earth, such as oxygen, nitrogen, and water undergo turnover or cycling through both the biotic (living) and abiotic (geological, atmospheric, and hydrologic) compartments of the Earth.
    • Ecosystems hinge on biogeochemical cycles.
    • The nitrogen cycle, the phosphorous cycle, the sulfur cycle, and the carbon cycle all involve assimilation of these nutrients into living things.
    • The atmosphere is considered a reservoir for nitrogen.
    • This flow from abiotic to biotic compartments of the Earth is typical of biogeochemical cycles.
  • Role of Microbes in Biogeochemical Cycling

    • Nutrients move through the ecosystem in biogeochemical cycles.
    • A biogeochemical cycle is a pathway by which a chemical element (such as carbon or nitrogen) circulates through the biotic (living) and the abiotic (non-living) factors of an ecosystem.
    • A good example of a molecule that is cycled within an ecosystem is water, which is always recycled through the water cycle.
    • The key collective metabolic processes of microbes (including nitrogen fixation, carbon fixation, methane metabolism, and sulfur metabolism) effectively control global biogeochemical cycling.
    • Consequently, chemical processing of nitrogen (or nitrogen fixation) is necessary to convert gaseous nitrogen into forms that living organisms can use.
  • Properties of Nitrogen

    • Nitrogen compounds were well known during the Middle Ages.
    • Nitrogen is a chemical element with symbol N and atomic number 7.
    • The nitrogen cycle describes the movement of the element from the air into the biosphere and organic compounds and back into the atmosphere.
    • Nitrogen is a nonmetal with an electronegativity of 3.04.
    • The triple bond in molecular nitrogen (N2) is one of the strongest known.
  • Nitrogenous Waste in Terrestrial Animals: The Urea Cycle

    • It is the main nitrogen-containing substance in the urine of mammals.
    • The body uses it in many processes, the most notable one being nitrogen excretion.
    • Urea is widely used in fertilizers as a convenient source of nitrogen.
    • Hence, the urea cycle is also referred to as the ornithine cycle.
    • The enzyme ornithine transcarbamylase catalyzes a key step in the urea cycle.
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