Nitrogen cycle Flashcards
in the nitrogen cycle microorganism are responsible for?
converting one form of nitrogen from another
Who can fix nitrogen (N2) ?
Only certain prokaryotes
Why only certain prokaryotes?
because N2 requires lot of energy to break the triple bond
how do nitrogen fixers live ?
free-living(cyano) or symbiotic (Rhizobium)
the nitrogen fixing the reaction is catalyzed by what ?
nitrogenase complex
how many electrons are required to fix nitrogen ?
8 electron
The electron come from what ?
pyruvate
are the 8 electron completely used?
No, 2 are lost as H2 in the process
Nitrogenase enzyme complex requires what to do so?
ATP,energy to break triple bond
Ammonia is the final what and is used for ?
product and is used to produce amino acids
Dinitrogenase reductase is inhibited by ?
the presence of oxygen
quick quick overview?
flavodoxin reduced donne electron et dinitrogenase reduced gives electron
name of Free-living nitrogen fixers?
- Azotobacter
- Beijerinckia
- Clostridium
Free-living nitrogen fixers are widespread?
in soil
free-living nitrogen fixers require?
a soil rich in organic matter to provide energy for nitrogen fixation
Free-living Nitrogen fixers produce?
ammonia that can be used by plants (NH3, dissolves in water to produce ammonium NH3)
Free-living nitrogen fixers that are strictly anaerobe?
Clostridium
Azotobacter are what?
strict aerobe,enzyme is protected by a very high rate of O2 consumption,keeps the intrtacellular environment anaerobic
all species of cyanobacteria are capable of N2 ?
no,
Cyanobacteria are what?
major nitrogen-fixing organisms in nature
Cyanobacteria produce energy by?
oxygenic photosynthesis, oxygen is produced in the cell.
le fait que azotobacter leur interieur est anae robic ca fait que ?
oxygen peut pas inhibiter nitrogen fixation
how can cyanobacteria fix nitrogen if they produce oxygen?
nitrogen fixation occurs in specialized anaerobic cells (heterocyts),which lack Photosystem 11 (does not produce O2)
the heterocysts have a thick cell wall that slow down ?
the diffusion of O2
The regular cells provide heterocytosts with?
carbohydrate (pyruvate )
