NITROGEN CYCLE

Most of the molecules used by biological systems it's contain nitrogen symbol N. The biological system including has proteins, chlorophyll, nucleic acids and vitamins and many other cellular constitution. In these are all compounds nitrogen is in it's reducing from with an oxidation number of - 3.The principal reservoir of nitrogen is (N₂) molecules in the atmosphere. Therefore, a major challenging to technology and biology involves the reduction of N₂ molecules for incorporating into essential nitrogen compounds.

                       The nitrogen cycle can be viewing as a set of enzymatically catalysed redox reactions and it's leading to an accessible supply of reduced nitrogen compounds. All microorganisms are almost entirely responsible for the interconversion of inorganic forms of the nitrogen element. The enzymes that's catalyse these conversations have Mo, Fe, and Cu at their activesites.

                              Although N₂ molecule is a most abundant constitute of the Earth's atmosphere and it's useful is limited by it's unreactivity. Although a smaller amounts of nitrogen molecule react with oxygen molecule under extremely conditions, such process providing only a small percentage of the nitrogen requirements of the biosphere. The remaining comes from the process of nitrogen fixation. The biological reduction of the nitrogen to ammonia is carried out and exclusively by prokaryotes, including both archaea. The enzyme system for nitrogen fixation is functions anaerobically and oxygen molecules irreversibly and rapidly destroys the enzyme. Nevertheless nitrogen fixation also occurred in aerobic bacteria. In addition and important association and symbiosis exit between higher plants and nitrogen -fixing bacteria such as rhizobia. In this symbiosis, bacteria that living within controlled environments in the plant, such as root nodules, having low level O₂. The plant's provides that bacteria with reducing carbon compounds from photosynthesis. While that bacteriaum providing fixed nitrogen to the plant.

                       A reduction potential about - 0.28 V is required for biological nitrogen fixation. The reduced ferredoxins or flavoprotiens with reduction potential of - 0.4 - 0.5 V are readily available in the biological system. These potential indicating that nitrogen fixation is thermodynamically feasible, this is not the case kinetically. The kinetic barrier to nitrogen molecule reduction apparently arises from the need to form bound intermediates in the conversion of N₂ to NH₄. All organisms invest metabolic energy from adenosine triphosphate (ATP) and hydrolysis for which ∆G≈−31 kj mol⁻¹ for conversion to ADP(adenosine diphosphate) and inorganic phosphate (P) to producing the key intermediate in the nitrogen fixation process.

                    The reduction of nitrogen molecule consumes 16 molecules of ATP for each molecule of nitrogen molecule is reduced. The most organisms capable of nitrogen fixation using available fixed nitrogen sources, ammonia, nitrite or nitrate and repress the synthesis of the elaborate nitrogen fixation system.

Once a nitrogen reduces, organisms incorporate the nitrogen into organic molecules, where it entires the biosynthetic pathways of the cell. When the organisms die and biomass decay, organonitrogen compounds decompose and release nitrogen to the environment in the form NH₄⁻ or NH₃ depending on the conditions.

              The growing, human population and it's dependence on synthetic fertilizers have had enormous impacts on the nitrogen cycle. Ammonia synthesis is carried out by the " HABER - BOSCH PROCESS" which augmented the total fixed nitrogen available to life on Earth. Between the third and half of every nitrogen fixed occurring through technological and agricultural, rather than the natural means. In addition to ammonia itself, nitrate salts are produced by industrially from ammonia for using fertilizers. Which is increasingly all segments of the natural cycle. The natural cycle reservations are inadequate sinks for the excess input. Under the conditions, nitrite or nitrate may accumulate as an undesirable component of ground water or produce eutrophication in lakes, river deltas, wetlands, and coastal areas.