L10: Nitrogen cycle

Question 1

Nitrogen importance + caviat

Answer 1

must abunfant gas, key in nucelotides, amino acids, protein, cholorphyll. Only ammonium is bioavailable.

Question 2

Nitrogen Flux

Answer 2

• fluxes between gasius in water + atmosphere and biological molecule.
• but UNLIKE carbon, there is resevoir of non-N2 inorganic nitrogen (ammonim, nitrate)

Question 3

Define: nitrification, DNRA, ANRA

Answer 3

nitrification: ammonia to nitrae through ammonia/nitrite oxidation.

DNRA: disimialrity nitrate reduction to ammonium
ANRA: assimiatory nitrate reduction to ammonium

Question 4

Name 8 key nitrogen cycle pathways

Answer 4

1. Nitrogen fixation
   2.Nitrification
   3.Anammox
   4.Ammonum assimilation
   5.assimilatory reduction to ammonum ANRA
   6.ammnofication
   7.denitrifcation
   8.DNRA

Question 5

What is the ammonium vs nitrate trade off

Answer 5

ammonium only can be assimilated but orgaisings use ANRA to make nitrate
high level of ammonia re toxic but high nitrate is not
beacuse of nitirgication in soil, available ammonium is oxidises
ammonia binds to soil=less access

Question 6

Agriculture

Answer 6

1. Nfixing bac form root nodules. bac provide nitrogen, plant provides carbs
2. manure + dead plant conntirnute to N in soil
3. ammonium oxi makes nitrate which goes to grounwater
4. fertislies have ammonia + nitrata

Question 7

Consequences of nitrate leaching

Answer 7

• N is limting when there is a lot there is eutrophication
• leads to rapid plant + microbial growth = more biomass then it all dies
• dead biomass = decompostion = takes all oxygen
• aeornbes die
• oxygen minum zones had intense agriculural run off

Question 8

N2O emissions

Answer 8

incomplete denitifraction by dentirifces = nitrous oxide which is bery bad

Question 9

Nitrogren fixation

Answer 9

nitrogen gas to ammoim for biomass
by diazotophs
- big energy (sun maybe) needed + big e-
- key enzyme: nitrogenase which is O senstive

Question 10

Nitrifcation

Answer 10

• ammonum as ED to power ETC
• O is TEA. two options
  1. 2 steps of nitircation
  2. complete ammonia oxidation

key enzymes: ammonium monosygease + nitrate oxidoreductase

Question 11

anamox, define anamozisome

Answer 11

anaeorbic ammonium oxidation
- plactomecy oxides ammonia using nitrate as TEA
- most green house gas
- produces hyzaderine intermediate - rocket fuel

define: special membrane compartedm to contain reaction

Question 12

Ammonia assimilation + ANRA

Answer 12

to the biomass
1…
- ammonium to biomass
- most organisms can do it
- GS/GOGAT enzyme ecomple
2…
- nitrate to biomass
- nitrate reduced to ammonium

Question 13

Ammonification

Answer 13

• biomass to ammonium
• commond decompostion
• uses N molecules as ED
• if too much in cell goes to encrionment

Question 14

Dentifrication + DNRA

Answer 14

what happens when nitrate uses as TEA in anaeobic
1..
- includes 4 recutions
- nitrogen lost to enironmnet as N2
- incomplete defnitication = nitrous gas
2…
- 2 reeduction
- nitgoen retained in habitat
- needs more e- (more competive in e- rich/carbon rich plaxes)