Nitrogen cycle

• What is the purpose of the nitrogen cycle 


  Plants cannot obtain nitrogen directly from the air, nitrogen must be fixed into soluble inorganic nitrogen compounds
• what is nitrogen fixation 


  Nitrogen fixing bacteria like Rhizobium contains the enzyme nitrogenase which combines atmospheric nitrogen and hydrogen to form ammonia
• What are the two bacteria involved in nitrogen fixation

  Rhizobium and Azotobacter
• What is Azotobacter

  A free living bacteria found in the soil
• What is Rhizobium and where is it found

  Mutualistic bacteria found in the nodules on the roots of leguminous plants (peas)
• Why is Rhizobium bacteria a mutualistic bacteria

  Rhizobium uses nitrogen to produce amino acids and it supplies to the plant, and the plant provides Rhizobium with carbohydrates from photosynthesis
• what two types of nitrogen fixing bacteria can you have

  Free living or mutualistic
• What is ammonification


  Process where decomposers like fungi convert nitrogen containing molecules in dead organisms into ammonium compounds
• What is nitrification

  The process where ammonium compounds are converted into nitrites and then nitrates carried out by nitrifying bacteria
• What nitrifying bacteria oxides ammonium ions into nitrites

  Nitrosomonas bacteria
• What nitrifying bacteria oxidises nitrites into nitrates

  nitrobacter bacteria
• Where does nitrifying bacteria obtain its energy from

  They utilise the energy released from the oxidation reactions
• What is dentrification

  Th process where nitrates are converted back into nitrogen gas
• When does dentrification occur

  Where there is no oxygen normally in waterlogged soil
• Why is dentrification bad

  It reduces availability of nitrogen containing compounds so the soil need to be kept well aerated
• Is denitrifying bacteria an oxidation or reduction reaction

  Reduction reaction
• What are the reactants for Rhizobium and Azotobacter

  Nitrogen gas and hydrogen ions
• What do plants converts nitrates to

  Amino acids