nitrogen

Examples of nitrogen 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 .
  • Nitrogen enters the living world from the atmosphere via nitrogen-fixing bacteria.
  • This nitrogen and nitrogenous waste from animals is then processed back into gaseous nitrogen by soil bacteria, which also supply terrestrial food webs with the organic nitrogen they need.

• 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.

• 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.
  • De-Nitrification: Nitrogen in its nitrate form (NO3-) is converted back into atmospheric nitrogen gas (N2) by bacterial species such as Pseudomonas and Clostridium, usually in anaerobic conditions.
  • Describe the nitrogen cycle and how it is affected by human activity

• Properties of Nitrogen

  • Nitrogen in its elemental form is a non-metallic gas that makes up 78 percent of Earth's atmosphere.
  • Nitrogen compounds were well known during the Middle Ages.
  • Nitrogen is a chemical element with symbol N and atomic number 7.
  • Nitrogen is a nonmetal with an electronegativity of 3.04.
  • The triple bond in molecular nitrogen (N2) is one of the strongest known.

• 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.

• 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.

• Stereogenic Nitrogen

  • A close examination of the ephedrine and pseudoephedrine isomers suggests that another stereogenic center, the nitrogen, is present.
  • Since the nitrogen in these compounds is bonded to three different groups, its configuration is chiral.
  • However, pyramidal nitrogen is normally not configurationally stable.
  • If the nitrogen atom were the only chiral center in the molecule, a 50:50 (racemic) mixture of R and S configurations would exist at equilibrium.
  • In any event, nitrogen groups such as this, if present in a compound, do not contribute to isolable stereoisomers.

• Early Discoveries in Nitrogen Fixation

  • Nitrogen fixation carried out by bacteria helps farmers yield healthy crops.
  • Hermann Hellriegel (1831-1895), a noted German agricultural chemist, discovered that leguminous plants took atmospheric nitrogen and replenished the ammonium in the soil through the process now known as nitrogen fixation.
  • He found that the nodules on the roots of legumes are the location where nitrogen fixation takes place.
  • Hellriegel did not determine what factors in the root nodules carried out nitrogen fixation.
  • These rhizobia perform the chemical processes of nitrogen fixation.

• Genetics and Regulation of N2 Fixation

  • Through control of gene expression, nitrogen fixing bacteria can turn on and off the proteins needed for nitrogen fixation.
  • The fixation of atmospheric nitrogen (N2) is a very energy intensive endeavor.
  • The nif genes are responsible for the coding of proteins related and associated with the fixation of atmospheric nitrogen into a form of nitrogen available to plants.
  • These genes are found in nitrogen fixing bacteria and cyanobacteria.
  • Discuss the role of the nif genes in controlling nitrogen fixation

• Nitrogen Compounds

  • The nitrogen-nitrogen triple bond in N2 contains 226 kcal/mol of energy, making it one of the strongest bonds known.
  • When nitrogen gas is formed as a product from various reactions, the bond energy associated with the N-N triple bond is released, causing the explosive properties seen in many nitrogen compounds.
  • This is one of a variety of nitrogen oxides that form a family often abbreviated as NOx.
  • Nitrogen triiodide (NI3) is an extremely sensitive contact explosive.
  • In all cases, the explosive properties of nitrogen compounds are derived from the extreme stability of the product of these reactions: gaseous molecular nitrogen, N2.