2-3 Nitrogen Cycle

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2-3 Nitrogen Cycle
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Nitrogen Cycle

• Nitrogen production of proteins and nucleic
  acids
• 79 of atmosphere N2 gas
• Most plants and animals cannot capture nitrogen
  from the atmosphere
• Plants Use nitrogen in the form of NO3-
  nitrates to produce amino acids then proteins
• Animals eat plant protein ? digest it into amino
  acid ?use amino acids to build animal protein in
  the cells

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Nitrogen Cycle
Nitrogen Fixation
Denitrification
Nitrification
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Nitrification

• Animals produce waste, die and decay
• Nitrogen compounds introduced to soil
• Bacteria work on compounds breaking them into
  ammonium compounds then nitrates
• Nitrates are absorbed by plants

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Nitrogen Fixation

• Nitrogen Fixation process of converting
  atmospheric N2 into nitrates (NO3-) and ammonium
  ions (NH4)
• Nitrogen-fixing bacteria found on nodules of
  roots (legumes, alfalfa)
• Rhizobium
• convert N2 to nitrates to be used by plant
• plant gives bacteria sugars
• excess nitrates move into soil

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Nitrogen Fixing Bacteria
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Rhizobium
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Nitrogen Fixation

• Lightning - N2 reacts with O2 - Nitrates are
  produced
• Nitrates fall to earth, enter soil, move into
  plants through the roots
• Crop rotation - balances input and output of N2

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Denitrification

• Denitrifying bacteria break down nitrates and
  nitrites into N2 gas
• gas reenters atmosphere
• Denitrifying bacteria carry out anaerobic
  respiration ? found in tightly packed soil and or
  water logged soil
• Aeration slows down denitrification
• Allow oxygen entry to soil ?inhibits denitrifying
  bacterial growth
• Keeps grass green by keeping nitrates in the soil
• Nitrates are need for chlorophyll (protein)
  production

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Nitrogen Cycle Diagram
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1 Atmospheric pool of nitrogen2
Nitrogen-fixing bacteria in root nodules of
legumes3 Fertilizers4 Soil nitrate5
Nitrate take up by plant roots6 Plant and
animal proteins7 Dead organisms8
Decomposers9 Nitrate bacteria10 Nitrate
bacteria11 Denitrifying bacteria12
Lightning
Nitrogen Cycle Diagram