NITROGEN

• DIFFERENT FORMS OF NITROGEN IN THE NITROGEN CYCLE?

  • NH4+ : ammonium ions
  • NO2- : nitrite ions
  • NO3- : nitrate ions
  • N2 : nitrogen gas in atmosphere
  • amine groups in AAs in consumers
• HOW ARE NH4+ CONVERTED TO NO2-?

  nitrification
• HOW ARE NO2- CONVERTED TO NO3-?

  nitrification
• HOW ARE NH4+ CONVERTED TO NO3-?

  nitrification
• HOW ARE NO3- CONVERTED INTO N2?

  denitrification
• HOW IS N2 CONVERTED TO NH4+?

  nitrogen fixation by free-living bacteria
• HOW IS N2 CONVERTED INTO NH4+ CONTAINING MOLECULES IN PRODUCERS?

  nitrogen fixation by mutualistic bacteria
• HOW ARE NO3- CONVERTED INTO NH4+ CONTAINING MOLECULES IN PRODUCERS?

  absorption
• HOW ARE NH4+ CONTAINING MOLECULES IN PRODUCERS CONVERTED TO AMINE GROUPS IN AAS IN CONSUMERS?

  feeding and digestion
• HOW ARE AMINE GROUPS IN AAS IN CONSUMERS CONVERTED TO NH4+ CONTAINING MOLECULES IN SAPROBIONTS?

  death and excretion
• HOW ARE NH4+ CONTAINING MOLECULES IN PRODUCERS CONVERTED INTO NH4+ CONTAINING MOLECULES IN SAPROBIONTS?

  death
• HOW ARE NH4+ CONTAINING MOLECULES IN SAPROBIONTS CONVERTED INTO NH4+ IONS?

  ammonification
• KEY PROCESSES IN THE NITROGEN CYCLE?

  • nitrogen fixation
  • nitrification
  • denitrification
  • ammonification
  • absorption
  • feeding/ digestion
  • death/ excretion
• AMMONIFICATION?

  • producing ammonia from organic nitrogen-containing compounds
  • e.g. urea, proteins, nucleic acids, vitamins
  • saprobionts feed on faeces and dead organic materials
  • releases ammonia
  • forms ammonium ions in soil
• NITRIFICATION?

  • oxidation reaction
  • releases energy
  • converting ammonium ions into nitrite ions
  • and nitrite ions into nitrate ions
  • using nitrifying bacteria
  • aerobically respire, therefore oxygen is required
• NITROGEN FIXATION?

  • converting nitrogen gas into nitrogen-containing compounds
  • industrially or naturally (lightning)

  FREE-LIVING NITROGEN-FIXING BACTERIA

  • reduce nitrogen gas into ammonia
  • used for AAs
  • release nitrogen-rich compounds when they die and decay
  • aerobically respire

  MUTUALISTIC NITROGEN-FIXING BACTERIA

  • found in nodules of roots of legumes
  • obtain carbohydrates from plants
  • plants get AAs from bacteria
  • aerobically respire
• DENITRIFICATION?

  • convert nitrates in soil into nitrogen gas
  • denitrifying bacteria
  • anaerobic respiration
  • found in waterlogged soil
  • with low oxygen concentration