Nitrogen Cycle

Question 1

what are the methods of nitrogen fixation

Answer 1

Lightning
- breaks N#N triple bond by binding nitrogen with oxygen -> this rains down as nitrates
Haber Process
- heightens the temperature and pressure -> nitrogen binds to hydrogen NH4+ or NH3
biological fixation
- azotobacter -> convert nitrogen and hydrogen NH4
- FREE LIVING IN SOIL
- used in protein synthesis and leach into the soil
- Rhizobium -> symbiosis in root nodules of legumes
- nitrogen reduced to NH4+ using nitrogenase (anaerobic)
- leghaemoglobin to remove oxygen carried away from the nodule

Question 2

NH4+ -> NO2-

Answer 2

nitrification carried out by the nitrosomonas (oxidation carried out in aerobic conditions)

Question 3

NO2- -> NO3-

Answer 3

nitrification carried out by the nitrobacter (oxidation carried out in aerobic conditions)

Question 4

food chain -> NH4

Answer 4

ammonification - saprobionts & detritivores break down proteins into NH4+

Question 5

NO3- -> N2

Answer 5

denitrification carried out by pseudomonas
- anaerobic bacteria (water logged soil)

Question 6

which plants are able to fix nitrogen

Answer 6

legumes (Rhizobium) symbiosis in the root nodules

Question 7

explain the advantage of plants being able to fix their own nitrogen

Answer 7

• symbiosis with rhizobium
• convert N2 into ammonium
• used in protein synthesis