Most of the nitrogen is in the form of amino acids in protein.
"Environmental Chemistry: A Global Perspective", 4e - Gary W. VanLoon & Stephen J. Duffy

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Most of the nitrogen is in the form of amino acids in protein.
"Environmental Chemistry: A Global Perspective", 4e - Gary W. VanLoon & Stephen J. Duffy
Nitrogen Cycle
Make sure you know these terms:
nitrogen fixation: the process by which nitrogen in the air (N2) is converted into ammonium or nitrate, which are usable forms by plants and animals
ammonification: the breaking down of ammonia into nitrates by decomposers
assimilation: the easy uptake of nitrates or ammonium by plants
denitrification: the process by which nitrates and nitrites are fixed by denitrifying bacteria in the soil and returned to the atmosphere
nitrification: the oxidation of ammonium to nitrite to nitrate
not much, but outlining the cycle. sorry about the weasel to any weasel fans :(