Nitrogen cycle

Nitrogen cycle

1. The nitrogen cycle ensures that nitrogen within these organic molecules in the biosphere is constantly recycled so that it may be used

2. Saprobiotic nutrition; breaking down dead organisms. Decomposers break down solid organic matter into soluble substances, first step in the decay of dead organisms

3. AMMONIFICATION; ammonia from urea and amino acids. Decomposers and other microorganisms are also involved in the conversion of organic nitrogen-containing compounds in urea and amino acids into ammonia. This process is called ammonification. Ammonia can be lost to the atmosphere, taken up by plants as ammonium ions, or converted to other forms of nitrogen.

4. NITRIFICATION; ammonium ions (in soil and water) are oxidised to nitrites and nitrates by nitrifying bacteria. Nitrification requires oxygen, so it happens most rapidly in well aerated soil or well oxygenated bodies of water. The nitrate ions produced by nitrification can be taken up by plants and used to make proteins.

5. NITROGEN FIXATION; nitrogen to nitrogen compounds. Before plants and animals can use nitrogen, it must first be converted to absorbable nitrogen compounds. This is called nitrogen fixation and occurs during thunderstorms. Lightening provides the energy to oxidise nitrogen --> nitrogen oxides. The fixation is carried out by nitrogen - fixing bacteria. Some live free in the soil or water. Nitrogen - fixing bacteria passes an enzyme that enables them to reduce nitrogen to ammonia or ammonium compounds.

6. DENITRIFCATION; nitrates back to nitrogen. The nitrogen cycle is completed by denitrifying bacteria which live in conditions of low oxygen and reverse the nitrifying process, converting nitrates to nitrites, and nitrites into nitrogen gas. The process is called denitrification and leads to the loss of nitrogen from the biotic component of an ecosystem to the atmosphere.