The nitrogen cycle

• How is nitrogen important

  • atmosphere contains 78% nitrogen - very unreactive and can't be used directly by plants or animals
  • nitrogen needed for making proteins for growth
  • plants get nitrogen from soil - nitrogen in air has to turn to nitrogen compounds before plants can use it. Animals only get protein from eating plants
• what is the nitrogen fixation and the 2 ways it can happen?

  • process of turning N2 from air to nitrogen compound in soil which plant can use
  • Lightning - so much energy in a bolt of lightning - enough to make nitrogen react with oxygen in air to give nitrates
  • Nitrogen- fixing bacteria - in soil and the roots of some plants
• what are the 4 different types of bacteria involved in the nitrogen cycle?

  • Decomposers - breaks down proteins and urea and turns them into ammonia which forms ammonium ions in the soil
  • Nitrifying bacteria - turns ammonium ions in decaying matter into nitrates
  • Nitrogen-Fixing bacteria - turns atmospheric N2 into nitrogen compounds that plant can use
  • Denitrifying bacteria - turns nitrates back into N2 gas