Nitrogen cycle

Nitrogen cycle

1. The nitorgen cycle ensures that nitrogen bound up 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 compunds 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. Nirtification ; ammonium ions (in soil and water) are oxidises to nitrites and nitrates by nitrifying bacteria. These bacteria are chemoautotrophs, obtaining energy from the redox reactions involved in nitrification. Nitrification requires oxygen, so it happens most rapidly in well aerated soil or well oxygenated bodyies 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 coumpounds. Before plants and animals can use nitorgen, it must first be converted to absorbable nitrogen compounds. This is called nitrogen fixation. A little nitrogen fixation occurs during thunderstorms. Lightening provides the energy to oxidise nitrogen to nitrogen oxides. More than 95% of nitrogen fixation takes place biologically. The fixation is carried out by nitrogen - fixing bacteria. Some live free in the soil or water, whereas others live mutualistically in root nodules of leguminous plants. Nitogen - fixing bacteria passes nitogenase, an enzyme that enables them to reduce nitrogen to ammonia or ammonium compounds

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