Three oxides form naturally from atmospheric nitrogen: nitrogen dioxide (NO2), nitric oxide (NO) and nitrous oxide (N2O). These oxides form when lightning generates enough heat to promote reactions between nearby nitrogen and oxygen molecules.
Lightning often occurs during a thunderstorm, so the oxides catalyzed by lightning may come into contact with water. The result is another oxygen derivative called nitric acid (HNO3).
Blue-green algae and bacteria use nitrogen gas to effect the synthesis of another nitrogen derivative called ammonia (NH3). This process, called nitrogen fixation, typically takes place in legume nodules.
Nitrogen enters into the composition of various salts called nitrates, nitrites and nitrides. For example, the nitric acid formed in the atmosphere enters the soil and reacts with ammonia to form a salt called ammonium nitrate. Other nitrates also form naturally, such as sodium nitrate, an abundance of which occurs in the Atacama Desert of Chile.
Plants cannot use atmospheric nitrogen directly, but they assimilate the nitrogen derivatives provided by lightning and nitrogen-fixing organisms. Animals indirectly profit from these same nitrogen derivatives, either by eating plants or by eating herbivorous animals. Plant and animal cells use the nitrogen they thus acquire to synthesize further nitrogen derivatives, such as amines. Amines are altered ammonia molecules in which organic groups replace at least one of the three hydrogen atoms. The substituent may be a methyl group (-CH3), a carbon ring or a carbon chain.
Plant and animal cells also synthesize complex nitrogen derivatives called proteins. In addition to nitrogen, proteins contain carbon, hydrogen, oxygen and sometimes sulfur. Structural proteins serve as components of plant and animal tissue. Proteins called enzymes serve as catalysts for chemical reactions in plant and animal cells.
Some nitrogen derivatives synthesized by plant and animal cells contain phosphorus. ATP, NADPH, RNA and DNA are significant examples. ATP and NADPH provide energy for cellular reactions. DNA contains the genes controlling life processes. RNA assists in the synthesis of proteins.
Chemical laboratories synthesize many carbon derivatives, such as nitriles and azo compounds. Nitriles are compounds containing a carbon atom united with a nitrogen atom by a triple bond. Azo compounds contain two adjacent nitrogen atoms linked by a double bond.