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NitrogenFixation

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NitrogenFixation

Biological Abiological

S mbioticNon

Industrial Natural

ym ot c

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Abiological nitrogen fixation

In abiological nitrogen fixation the nitrogen is reduced to ammonia

without involving any living cell.

Abiological fixation can be of two types : industrial and natural.

For example, in the Habers process, synthetic ammonia is produced by

passing a mixture of nitrogen and hydrogen through a bed of catalyst

(iron oxides) at a very high temperature and pressure.

In natural process nitrogen can be fixed especially during electrical

discharges in the atmosphere.

It may occur during lightning storms and nitrogen in the atmosphere

can combine with oxygen to form oxides of nitrogen.

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Biological nitrogen fixation

ammonia in the presence of nitrogenase.

Biological Nitrogen FixationBiological Nitrogen Fixation

SymbioticSymbiotic Non SymbioticNon Symbiotic

Root noduleRoot noduleEnz me ActionEnz me Action

ormat onormat on

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Nitrogenase is a biological catalyst found in some microorganisms.

-

Azospirillum andAzotobacter.

Biological nitrogen fixation is brought about bath by free-living soil

microorganisms and by symbiotic associations of microorganisms with

higher plants.

Leguminous plants fix atmospheric nitrogen by working symbiotically with

special bacteria, rhizobia, which live in the root nodules.

Rhizobia infect root hairs of the leguminous plants and produce the nodules.

The nodules become the home for bacteria where they obtain energy from

the host plant and take free nitrogen from the soil air and process it into

combined nitrogen.

n return, t e p ant rece ves t e xe rom no u es an pro uces oo

and forage protein.

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Mechanism of biological nitrogen fixation

Nitrogen fixation requires:

i. The molecular nitrogen

ii. A strong reducing power to reduce nitrogen like FAD (Flavin

adenine Dinucleotide

iii. Source of energy (ATP) to transfer hydrogen atoms to dinitrogen and

iv. Enzymes nitrogenase and Legheamoglobin

v. ompoun or trapp ng t e ammon a orme s nce t s tox c to ce s.

vi. The reducing agent and ATP are provided by photosynthesis and

.

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