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Nitrogen Cycle IGCSE Biology Edexcel
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Biological compounds that contain Nitrogen :
proteins |
vitamins |
DNA |
RNA |
ATP |
chlorophyll |
amino acids |
What happens after nitrogen fixation
Assimilation |
into plants as proteins |
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into bacteria as proteins |
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into animals after feeding on plants |
Nitrification by nitrifying bacteria to make nitrite and nitrate ions |
Nitrates will be assimilated into plants as proteins after being absorbed in the soil by active transport through root hair cells |
nitrates might be denitrified by denitrifying bacteria |
decomposition
Animals , plants and bacteria excrete nitrogenous waste |
Decomposers digest by extracelluar enzymatic digestion the nitrogenous waste products and dead remains into ammonia |
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Nitrogen Fixing Bacteria
Free in soil |
in root nodules |
convert nitrogen gas into ammonia that is used by bacteria to make amino acids and proteins |
found in leguminous plants e.g. peas , clovers |
When bacteria die , their proteins decompose and they release NH3 in the soil |
convert N2 to NH3 to be used to make amino acids, proteins and other compounds |
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when leguminous plants die , nitrogen containing compounds decompose releasing ammonia back |
2. Nitrification
nitrifying bacteria in the soil oxidise ammonia from nitrogen fixation to nitrite and then to nitrate ions |
Nitrate ions can be absorbed through active transport by plants to make amino acids and then proteins |
nitrate ions can be converted back to nitrogen by denitrifying bacteria |
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Lightning
oxidization of nitrogen that produces nitrogen oxides |
nitrogen oxides dissolve in rain water and enter the soil |
converted into nitrates by nitrifying bacteria |
Haber Bosch process
artificial nitrogen fixation |
nitrogen +hydrogen --> ammonia |
ammonia used to make fertiliser |
Denitrification
denitrifying bacteria in the soil convert nitrate ions back to nitrogen |
Feeding and assimilation
Feeding |
Assimilation |
animals feed on plants or on other animals that have fed on plants |
plants absorb nitrate ions by AT in the soil |
they digest animal or plant protein |
make amino acids |
assimilate the proteins in their body |
make proteins in the plant |
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also used to make chlorophyll, DNA |
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