nitrogen cycle

Question 1

what is nitrogen needed for

Answer 1

needed for growth and repair - in nucleic acid and protein synthesis

Question 2

what are the four stages of the nitrogen cycle

Answer 2

nitrogen fixation
nitrification
ammonification
denitrification

Question 3

explain nitrogen fixation

Answer 3

proccess that converts atmospheric nitrogen gas (N2) into nitrogen containing compounds like ammonia (NH3) (reduction) by:

1) free living bacteria = azotobacter fix N2 into NH3 and then amino acids

2)mutualistic/ symbiotic bacteria = Rhizobium use it for amino acids for plants and plants provide carbohydrates for them

3)abiotic processes = lightning, haber proccess

Question 4

where is Rhizobium bacteria found

Answer 4

in root nodules of legumes

Question 5

explain nitrification

Answer 5

ammonia (NH3) and ammonium ions NH4+ are first oxidised to nitrites (NO2-) by nitrosomonas bacteria.
then to nitrates (NO3-) by nitrobacter which plants can absorb and assimilate (oxidisation)

Question 6

explain ammonification

Answer 6

production of ammonia from urea, proteins, nucleic acids, vitamins found in dead organisms and faeces. NO3- into NH3 or NH4+

saprotrophs/ decomposers decompose these

Question 7

explain denitrification

Answer 7

process where nitrates (NO3-) is converted back into N2= nitrogen gas

-carried out by denitrifying bacteria
-occurs under anaerobic conditions e.g waterlogged soils
(reduction)