Nitrogen fixation is a process by which nitrogen is taken from its natural, relatively inert molecular form (N2) in the atmosphere and converted into nitrogen compounds (such as ammonia, nitrate and nitrogen dioxide) either by physical means or biological means. In biological nitrogen fixation atmospheric nitrogen is converted to ammonia by a pair of bacterial enzymes called nitrogenase. It can be represented as N2+8H++8e−+16ATP→2NH3+H2+16ADP+16Pi