1. 2-3 Nitrogen Cycle

2. 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

3. Nitrogen Cycle
Nitrogen Fixation
Denitrification
Nitrification

5. 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

6. 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

7. Nitrogen Fixing Bacteria

8. Rhizobium

9. 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

10. 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

13. Nitrogen Cycle Diagram

14. Nitrogen Cycle Diagram
1 Atmospheric pool of nitrogen 2 Nitrogen-fixing bacteria in root nodules of legumes 3 Fertilizers 4 Soil nitrate 5 Nitrate take up by plant roots 6 Plant and animal proteins 7 Dead organisms 8 Decomposers 9 Nitrate bacteria Nitrate bacteria Denitrifying bacteria Lightning