Nitrogen is present in
the protein and nucleic
acids in plants.
Nitric acid is formed
when oxides of
nitrogen react with
water in the
atmosphere.
The Nitrogen
Cycle
Chemosynthetic
organisms obtain the
energy for fixing
carbon dioxide from
the conversion of
nitrite to nitrate.
Nitrogenous fertilizers
are made from
ammonia by an
industrial process.
Burning fuels produces
polluting oxides of
nitrogen.
The enzyme
nitrogenase converts
nitrogen into ammonia.
The ammonia is then
converted into protein.
denitrification
nitrogen fixation
nitrification
industrial fixation
Nitrogen in the
atmosphere
Nitrites (NO2-)
Nitrates (NO3-)
Ammonium (NH4+)
lightning
Free-living blue-green
algae and bacteria in
the soil.
Symbiotic blue-green
algae and bacteria in
nodules of legumes.
Nitrate is taken in by
root hair cells and
transported to growing
points.
Lightning acts on
oxygen and nitrogen
producing oxides of
nitrogen.
Nitrogen and hydrogen
are reacted together
in the Haber process,
producing ammonia.
Proteins are
decomposed via amino
acids to ammonia.
runoff
defaecation
excretion
Denitrifying bacteria
use nitrate as an
electron acceptor in
anaerobic conditions.
Rain washes soluble
nitrates out of soils
into rivers and oceans.
Nitrogenous fertilisers
are applied to fields to
enhance crop growth.
absorption
assimilation
decay
ammonification
denitrifying bacteria
death
Nitrogen is present in
the protein and nucleic
acids in animals.
Chemosynthetic
organisms obtain the
energy for fixing
carbon dioxide from
the conversion of
ammonium to nitrite.