Search results
Results from the WOW.Com Content Network
Nitrogen-14 is the source of naturally-occurring, radioactive, carbon-14. Some kinds of cosmic radiation cause a nuclear reaction with nitrogen-14 in the upper atmosphere of the Earth, creating carbon-14, which decays back to nitrogen-14 with a half-life of 5700(30) years .
Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many drugs are mimics or prodrugs of natural nitrogen-containing signal molecules: for example, the organic nitrates nitroglycerin and nitroprusside control blood pressure by metabolising into nitric oxide.
A large fraction of the chemical elements that occur naturally on the Earth's surface are essential to the structure and metabolism of living things. Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [1]
It occurs naturally in the air by means of NO x production by lightning. [6] [7] Nitrogen fixation is essential to life on Earth because fixed inorganic nitrogen compounds are required for the biosynthesis of all nitrogen-containing organic compounds such as amino acids, polypeptides and proteins, nucleoside triphosphates and nucleic acids.
Abundance (atom fraction) of the chemical elements in Earth's upper continental crust as a function of atomic number; [5] siderophiles shown in yellow Graphs of abundance against atomic number can reveal patterns relating abundance to stellar nucleosynthesis and geochemistry.
Most biological nitrogen fixation occurs by the activity of molybdenum (Mo)-nitrogenase, found in a wide variety of bacteria and some Archaea. Mo-nitrogenase is a complex two-component enzyme that has multiple metal-containing prosthetic groups. [22] An example of free-living bacteria is Azotobacter.
Nitrate salts are found naturally on earth in arid environments as large deposits, particularly of nitratine, a major source of sodium nitrate. Nitrates are produced by a number of species of nitrifying bacteria in the natural environment using ammonia or urea as a source of nitrogen and source of free energy.
Nitrogen is the most critical element obtained by plants from the soil, to the exception of moist tropical forests where phosphorus is the limiting soil nutrient, [36] and nitrogen deficiency often limits plant growth. [37] Plants can use nitrogen as either the ammonium cation (NH 4 +) or the anion nitrate (NO 3 −).