nitrogen cycle

Examples of nitrogen cycle in the following topics:

• 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.

• 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.

• 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.

• Nitrogenous Waste in Birds and Reptiles: Uric Acid

  • Excess nitrogen is excreted from the body.
  • Nitrogenous wastes tend to form toxic ammonia, which raises the pH of body fluids.
  • The production of uric acid involves a complex metabolic pathway that is energetically costly in comparison to processing of other nitrogenous wastes such as urea (from the urea cycle) or ammonia; however, it has the advantages of reducing water loss and, hence, reducing the need for water.
  • It contains four nitrogen atoms; only a small amount of water is needed for its excretion.
  • Nitrogenous waste is excreted in different forms by different species.

• The Water (Hydrologic) Cycle

  • The water cycle is also essential for the maintenance of most life and ecosystems on the planet.
  • There are various processes that occur during the cycling of water, which include the following :
  • The water cycle is driven by the sun's energy as it warms the oceans and other surface waters.
  • Rain and surface runoff are major ways in which minerals, including carbon, nitrogen, phosphorus, and sulfur, are cycled from land to water.
  • The cycle is complete when surface or groundwater reenters the ocean.

• Connecting Proteins to Glucose Metabolism

  • When the amino group is removed from an amino acid, it is converted into ammonia through the urea cycle.
  • Thus, urea is the principal waste product in mammals produced from the nitrogen originating in amino acids; it leaves the body in urine.
  • The keto acid can then enter the citric acid cycle.
  • When deaminated, amino acids can enter the pathways of glucose metabolism as pyruvate, acetyl CoA, or several components of the citric acid cycle.
  • For example, deaminated asparagine and aspartate are converted into oxaloacetate and enter glucose catabolism in the citric acid cycle.

• Biogeochemical Cycles

  • The elemental components of organic matter are cycled through the biosphere in an interconnected process called the biogeochemical cycle.
  • The components of organic molecules are constantly being stored and recycled as part of their biogeochemical cycle.
  • Nitrogen, a major component of our nucleic acids and proteins, is critical to human agriculture.
  • The cycling of all of these elements is interconnected.
  • For example, the movement of water is critical for the leaching of nitrogen and phosphate into rivers, lakes, and oceans.

• The Phosphorus Cycle

  • Excess phosphorus and nitrogen that enters these ecosystems from fertilizer runoff and from sewage causes excessive growth of microorganisms and depletes the dissolved oxygen, which leads to the death of many ecosystem fauna, such as shellfish and finfish.
  • Phosphate dissolved in ocean water cycles into marine food webs.
  • Dead zones occur when phosphorus and nitrogen from fertilizers cause excessive growth of microorganisms, which depletes oxygen, killing flora and fauna.
  • Describe the phosphorus cycle and the effects of phosphorus on the environment

• Symbiosis between Bacteria and Eukaryotes

  • Prokaryotes fix nitrogen into a form that can be used by eukaryotes.
  • Nitrogen is usually the most limiting element in terrestrial ecosystems.
  • Atmospheric nitrogen, N2, provides the largest pool of available nitrogen.
  • Nitrogenase, the enzyme that fixes nitrogen, is inactivated by oxygen, so the nodule provides an oxygen-free area for nitrogen fixation to take place.
  • Through symbiotic nitrogen fixation, the plant benefits from using an endless source of nitrogen: the atmosphere.