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Flashcards in Nitrogen fixation Deck (20):

What ability of an organism do we focus on in nitrogen fixation

The ability to form ammonia from Nitrogen gas


Most abundant form of nitrogen? can it be used by organisms?

1. N2 Gas
2. cannot be utilized by most organisms


Which form of nitrogen is most efficient for uptake of nitrogen?

1. Ammonia
2. Nitrate


What form of nitrogen is easily passed from one organism to another through the food chain?

1. Amines
2. Nucleotides
3. Urea


What is process of nitrogen fixation?

The process by which nitrogen gas (N2) is reduced to ammonia by the enzyme nitrogenase and then converted into cellular material


What is the bulk of dinitrogen fixation?

The bulk is an enzyme driven process in prokaryotes referred to as diazotrophs (especially those that are symbiotic)


greatest contribution to the nitrogen cycle?

from the symbiotic species


Formula for nitrogen fixation? Is this process reduction or oxidation?

N2 + 8H+ + 6e- --> 2NH3 + H2 --> Cell synthesis
Dinitrogen Ammonia Proteins and nucleic acids
This entire process is nitrogen reduction


What does nitrogenase do?

it catalyes three reduction reactions to reach the end result of the production of ammonia


What does the nitrogenase reaction require ?
what type of process is it?

It requires
1. 8 protons
2. hydrolysis of 16 atp molecules
It is an energy intensive process.
intensive is requires a lot of work/effort


Explain the process by which fixed nitrogen is transferred from the free-living prokaryotes to other organisms

The process is not clear but it is possible that fixed nitrogen can be available when the diazotrophs are eaten or when they die and decompose.


Oxygen requirements of nitrogenase?
What conditions does it require?

1. its an oxygen sensitive enzyme
2. it requires anaerobic or extremely low oxygen conditions to be functional


Out of anaerobic, facultative anaerobic, or obligate aerobic organisms, which one would have an easy time doing nitrogen fixation?

Anaerobic organisms because they cannot survive in presence of oxygen, which means they dont need any special strategy for permitting nitrogen fixation.


Problem with facultative anaerobic and obligate aerobic organisms in nitrogen fixation?

they have to use oxygen for growth but also remove oxygen so that nitrogenase can function


How does facultative anaerobic and obligate aerobic organisms deal with their problems of nitrogen fixation

1. Rapid respiration of available oxygen before onset (beginning of ) for nitrogenase function
2. Sequestering (separation) of the microbes in symbiotic bacteria
3. the use of protective compounds to reduce the amount of available oxygen


What happens if synthetic nitrogen fertilizers are used improperly in excess?

They end up in run off from farms and pollute water bodies, where they can cause eutrophication and loss of oxygen


Which organism carries out nitrogen fixation?

Only certain prokaryotes.


Example of where to find nitrogen fixing organisms?

1. Freshwater ponds
2. Free living microorganisms ( anabaena, cyanobacterium)


What two types of bacteria are capable of nitrogen fixation?

Free living


Once nitrogenase results in the production of ammonia, what does the ammonia further get converted to in free-living diazotrophs? What pathway does this?

it gets converted to glutamine through the glutamine synthetase pathway and thus incorporated into cellular material.