the nitrogen cycle

Question 1

step 1 of nitrogen cycle

Answer 1

Nitrogen fixation
- occurs in azotobacter (free living bacteria in soil) or rhizobium (live inside root nodules of legume plants)
- bacteria contain nitrogenase enzyme which converts
N2 + 3H2 ———> 2NH3 (ammonia)

Question 2

what is fixed nitrogen in bacteria used to make?

Answer 2

a.a, proteins, DNA, RNA, ATP

Question 3

when the azotobacter bacteria die and decompose what is released?

Answer 3

NH3 and NH4+ ion back into soil (inorganic)

Question 4

what is step 2?

Answer 4

nitrification
- nitrosomonas bacteria used to make nitrites (NO2-)
- nitrobacter bacteria used to make nitrates (NO3-) from nitrites

Question 5

step 3

Answer 5

Ammonification (death + decomposition)
- nitrogenous molecules in plants eaten by animals and passed up food chain and excreted
- all of these molecules are decomposed and release NH3 or NH4+ back into soil

Question 6

step 4

Answer 6

denitrification
- denitrifying bacteria thrive under anaerobic conditions
- NOT BENEFICIAL
- convert useful nitrates back into N2 gas
- soil less fertile, reducing the nutrients status