What is the order of the nitrogen cycle

1. Nitrogen fixation.Fixing of free nitrogen into usable forms like nitrates. It is done either biologically by the nitrogen fixing bacteria or it is done industrially. Sometimes during lightening atmospheric fixation is also done. 
2.Assimilation: Nitrates in the surroundings are taken by plants and converted into plant proteins which are further taken by animals and converted into animal proteins. 
3.Ammonification: the dead parts of plants and animals along with their excreta are decomposed by bacteria and are converted into ammonium compounds in the soil. 
4.Nitrification: Ammonium compounds are oxidized to nitrites by nitrifying bacteria. These nitrites are further converted into nitrates by nitrobacter. 
5.De-nitrification: The nitrates are then converted into free N2 by denitrifying bacteria. This elementary N2 is then released in air.

Ithink the answer is nuclear membrane