209
nitrogen cycle
ent ammonia concentration is low. In anaerobic systems nitrates can act as electron acceptors for the oxidation of organic compounds (---7denitrification). In
this microbiological process nitrogen gas (N 2 ) is the main end product.
nitrification the process in which ammonia is oxidized by bacteria to nitrate,
---7nitrogen cycle.
nitrogen (N) the most abundant element in the atmosphere of the earth, as N2
gas (ca. 78 vol 0/0). Physical constants: mol. weight N2 28.016; density 1.2506
g dm- 3 (gas), 0.885 gcm- 3 (liquid); melting point -210 °C; boiling point -195
°C. Various forms of N compounds are present on earth, reduced forms as
NH 3 , N 2 H 4 , N3H, and oxidized forms as N 2 0, NO, N 2 0 3 , N 2 0 4 , and N 2 0 S •
Nitrogen is also an essential element in all living organisms. As building
atom in amino acids it is one of the main compounds of proteins. Some
organisms (some Bacteria and Cyanobacteria) can fIx atmospheric nitrogen. In this way they fertilize (eutrophicate) soils and waters with nitrogen
compounds. ---7nitrogen cycle.
nitrogen compounds inorganic or organic molecules which contain one or more
nitrogen atoms in their structure. Most naturally occurring inorganic nitrogen compounds in the atmosphere are nitrogen gas (N 2 ), with a relative
abundance of 78 0/0, and the gaseous nitrogen oxides N 2 0, NO, N0 2 . The
nitrogen oxides are partly produced by burning of fossil fuel and are
involved in the greenhouse effect as well as in the stratospheric ozone destruction. Another inorganic atmospheric nitrogen compound is ammonia (NH 3 ),
which indirectly contributes to the "acid-rain" problem. Inorganic, dissolved
forms of nitrogen compounds are nitrates (N0 3 -), and ammonium (NH/),
which can both be nitrogen sources for phytoplankton growth and thus be
responsible for the environmental problem of eutrophication. Important small
organic nitrogen compounds which can be found in nature as a consequence of anabolic or catabolic (---7metabolism) processes are urea, amines
and amino acids. Nitrogen atoms are present in all organisms (proteins, nucleic
acids).
nitrogen cycle biogeochemical cycle executed by various kinds of organisms in
which nitrogen is involved. In its most inert form, nitrogen gas makes up
most of the atmosphere. In living organisms, N is a major constituent of
amino acids, proteins, nucleic acids. However, despite the enormous amount of
nitrogen fixation which takes place, only a few highly specialized Bacteria and
many Cyanobacteria are able to extract nitrogen from air and turn it into biologically available compounds. Nitrogen gas is also fIxed by chemical reactions in the atmosphere and by industries. Conversely, nitrogen is lost to the
atmosphere by activities of Bacteria which reduce oxidized nitrogen compounds to nitrogen gas and various other volatile compounds (denitrification).
nitrogen cycle
ent ammonia concentration is low. In anaerobic systems nitrates can act as electron acceptors for the oxidation of organic compounds (---7denitrification). In
this microbiological process nitrogen gas (N 2 ) is the main end product.
nitrification the process in which ammonia is oxidized by bacteria to nitrate,
---7nitrogen cycle.
nitrogen (N) the most abundant element in the atmosphere of the earth, as N2
gas (ca. 78 vol 0/0). Physical constants: mol. weight N2 28.016; density 1.2506
g dm- 3 (gas), 0.885 gcm- 3 (liquid); melting point -210 °C; boiling point -195
°C. Various forms of N compounds are present on earth, reduced forms as
NH 3 , N 2 H 4 , N3H, and oxidized forms as N 2 0, NO, N 2 0 3 , N 2 0 4 , and N 2 0 S •
Nitrogen is also an essential element in all living organisms. As building
atom in amino acids it is one of the main compounds of proteins. Some
organisms (some Bacteria and Cyanobacteria) can fIx atmospheric nitrogen. In this way they fertilize (eutrophicate) soils and waters with nitrogen
compounds. ---7nitrogen cycle.
nitrogen compounds inorganic or organic molecules which contain one or more
nitrogen atoms in their structure. Most naturally occurring inorganic nitrogen compounds in the atmosphere are nitrogen gas (N 2 ), with a relative
abundance of 78 0/0, and the gaseous nitrogen oxides N 2 0, NO, N0 2 . The
nitrogen oxides are partly produced by burning of fossil fuel and are
involved in the greenhouse effect as well as in the stratospheric ozone destruction. Another inorganic atmospheric nitrogen compound is ammonia (NH 3 ),
which indirectly contributes to the "acid-rain" problem. Inorganic, dissolved
forms of nitrogen compounds are nitrates (N0 3 -), and ammonium (NH/),
which can both be nitrogen sources for phytoplankton growth and thus be
responsible for the environmental problem of eutrophication. Important small
organic nitrogen compounds which can be found in nature as a consequence of anabolic or catabolic (---7metabolism) processes are urea, amines
and amino acids. Nitrogen atoms are present in all organisms (proteins, nucleic
acids).
nitrogen cycle biogeochemical cycle executed by various kinds of organisms in
which nitrogen is involved. In its most inert form, nitrogen gas makes up
most of the atmosphere. In living organisms, N is a major constituent of
amino acids, proteins, nucleic acids. However, despite the enormous amount of
nitrogen fixation which takes place, only a few highly specialized Bacteria and
many Cyanobacteria are able to extract nitrogen from air and turn it into biologically available compounds. Nitrogen gas is also fIxed by chemical reactions in the atmosphere and by industries. Conversely, nitrogen is lost to the
atmosphere by activities of Bacteria which reduce oxidized nitrogen compounds to nitrogen gas and various other volatile compounds (denitrification).