Nitrogen Cycle terms to know
Nitrogen fixation
conversion of N2 into ammonia, and thence into proteins, is achieved by
microorganisms in the process called nitrogen fixation (or dinitrogen
fixation).
Denitrification
The biological reduction of nitrate to nitrogen gas by denitrifying bacteria in soil.
Occurs in oxygen poor environments
Nitrification
Oxidation of ammonium (NH4+) ions into nitrite (NO2-) ion and then nitrate
(NO3-) ions by microorganisms in soil and water. Nitrate ions are absorbed by the
plants as essential nutrients and, with the help of oxygen, converted (synthesized)
into plant protein (amino acids). See also nitration.
Assimilation
when a plant incorporates nitrogen into its tissues, making proteins and nucleic
acids
Ammonification
the conversion of organic nitrogen to ammonium (NH4+) by the action of
decomposers (bacteria). Occurs in oxygen poor environments
Ammonification is an important stage in the nitrogen cycle, a natural cycle which
makes the Earth's supply of this essential element available to living organisms. It
is carried out by a variety of microorganisms found in soil and water, which break
down proteins and amino acids in dead plant and animal matter, and feces,
releasing ammonia, which is usually retained in soil or water in the form of the
ammonium ion. Other groups of microorganisms then convert this into nitrate,
which can be absorbed by plants, maintaining the cycle. Ammonification is
therefore essential to all plant and animal life on the planet. In agriculture and
horticulture, the addition of compost and manure to soil provides an extra source of
nitrogen for ammonification
Ammonification is the process — carried out by a variety of microorganisms —
that breaks down proteins, amino acids, and other nitrogen-containing compounds
in dead and waste organic matter to form ammonia. Proteins are first split up into
amino acids, which are compounds containing an amine (NH2) group by bacteria
using enzymes known as proteases. The amino acids, and other compounds with
amine groups, such as nucleic acids and urea, are then decomposed by
microorganisms known as ammonifying bacteria, releasing ammonia (NH3). This
dissolves in water, and usually forms ammonium (NH4+) ions, by combining with
hydrogen (H+) ions, which are abundant in most soils. This ammonium is oxidized
to nitrites and nitrates by nitrifying bacteria, in the same way as nitrogen that has
been “fixed” from the atmosphere.