Question

C. Nitrogen-fixation (10 marks) Atmospheric nitrogen does not easily react with other chemicals to form new compounds. On the other hand nitrogen is a major macronutrient for living cells; it is found in amino and nucleic acids. Nitrogen fixation is the biological process by which atmospheric nitrogen is converted by certain microorganisms into ammonium and incorporated into biomass. 1. Write out the overall reaction of microbial nitrogen fixation and include the electron balance (ie. write out the # of electrons required during the bacterial nitrogen fixation process). (5 marks) 2. Search and post the chemical equation of the equivalent industrial Haber-Bosch process of human-made artificial nitrogen-fixation. Write in 3-4 sentences similarities or dissimilarities, if any, to the bacterial process. (3 marks) 3. Oxygen is a potent inhibitor of nitrogen-fixation. How do microbes circumvent the presence of atmospheric oxygen during the process of nitrogen fixation? (2 marks)

Answer 1

© Nitrogen fixation Microbial nitrogen fixation : oxidised ferredoxin reduced ferredoxin oxidised Fe protein reduced Fe protein 20 oxidised Mo Feprotein Reduced Mofe protein HN-NH HN-NU NH3 HNENU HN-nite Nitrogen fixation is the process by which molecular No is transfered into ammonia or related nitrogenous compounds => It is carried by naturally in soil by microorganisnis dire diazotrophy including 'Azabacter and archea. => of these symbiotic Rizobia (legume bacteria). Nonsymbiotic free such as Azotobactér, Clostridium, living bacterio blue-green algae

p. Haber-Bosch prown Nitrogen from air Nitrogen and Hydrogen 1:3 by volume 4 4-00-450c 200 atm iron catalyst onreacted Hydrogen from natural 999 90 Recycled gw are cooled and NHg turns to Liquid To storage - Industrial use. Reaction : In this process combines, atmospheric nitrogen 'with Nitrogen to produce NH3 Nyt 3t₂ = 2NH₂ sy The main sowice of hydrogen is from methane . -> catolipst called iron catalyst,out ? Lah Bulemperature and presswie. chis similarities; WBiological nitrogen fixation is done by milrogenases, but noboh - Bosch prowes is "perfored using molecular nit'rogen and hydrogen from natural gas."

los In bosch process catalyst is required " but in natural process no catalyst is required * In, nitrogen, fixation process, it mainly occurs' in anaerobic conditions, by drawing down oxygen levels, or binding the oxygen with protein st Nitrogenases are rapidly degraded by Joxygen as these are 'anaerobic organisms => It is very sensitive to oxygen so all the aerobic reactions are restricted to nitrogenases: