Nitrogen Fixation
Nitrogen Fixing bacteria reduce nitrogen gas
into ammonia:
N2 + 6H
2NH3
This reaction requires the enzyme nitrogenase
and requires a lot of energy
This is biological nitrogen fixation by microbes
Nitrogen Fixation
Nitrogen fixation can also happen by
industrial fixation. The Haber process
produces ammonia from the reaction of
nitrogen and hydrogen.
Nitrogen Fixation
Nitrogen fixation can also happen by
atmospheric fixation by lightning.
The energy in a lightning bolt can split
nitrogen molecules in the air, allowing each
nitrogen atom to react with oxygen to form
nitrogen oxides. The rain washes these
oxides to the ground, where they form
nitrates.
Nitrification
• Ammonia can be taken up directly by plants usually through their roots.
• However, most of the ammonia produced by
decay is converted into nitrates.
• This is accomplished in two steps: 1 type of
nitrifying bacteria oxidise NH3 to nitrite (NO2-).
• 2nd type of nitrifying bacteria convert the
nitrites to nitrate (NO3-).
Active Transport
Nitrates are taken directly into a plant in
uptake by the roots.
ATP is used to open protein channels
allowing nitrates, even at low
concentrations, to be taken up via the
process of active transport so that it can be
used to make plant proteins.
Ammonification
Microbial saprobionts break down proteins in
detritus to make ammonia:
1. Break down into amino acid using protease
2. Then remove amino groups from amino
acids using deaminase
Feeding
Animals are able to gain proteins directly by
consuming plant proteins.
Denitrification
Denitrifying bacteria convert nitrates into N2
and NOx gases
This is a way that useful nitrogen is lost from
the soil