Nitrogen Cycle,Amino acids, Proteins, Enzymes, Nucleotides and Nucleic acids,Prokaryotes,Atmospheric, Biological and Industria

Scholarships Dictionary Visa Details Study Abroad Exam Results Online Test Jobs

	Home
Biosphere Biosphere Introduction Matter and Energy Recycling of Materials - Biogeochemical Cycle Carbon Cycle Green House Effect

Home >> Biology >> Biosphere >> Nitrogen Cycle

Your Ad Here

3. Nitrogen Cycle

Nitrogen is a component of amino acids, proteins, enzymes, nucleotides and nucleic acids which form structural and functional constituents of living protoplasm. N₂ is picked in raw form and is changed into organic form by plants and some prokaryotes. Plants pick up inorganic nitrogen either as nitrates or ammonium ions. From then it passes over to animals.
Atmosphere is the major source of nitrogen as 4/5^th of air is made of nitrogen in elemental form. This atmospheric nitrogen is changed to nitrogen compounds by a process called nitrogen fixation. It is of three types-Atmospheric, Biological and Industrial.

(a) Atmospheric.
O₂ combines with N₂ in photochemical and electrochemical reactions to produce nitrogen oxides. Some are added through rain water. It adds 35 mg/m²/yr of N₂.

(b) Biological nitrogen fixation,
Certain free living bacteria (Azotobacter, Clostridium, Beijerinekia), symbiotic bacteria (Rhizobium) and cyanobacteria

Nitrogen Cycle

(Anabaena, Nostoe, Aulosira, Tolypothrix) pick up atmospheric nitrogen reducing it to the level of ammonia. It adds 140-700 mg/m²/yr of nitrogen.

(c) Industrial nitrogen fixation.
It is produced industrially by combining nitrogen and hydrogen under high pressure and low temperature (Heber’s process).

Nitrate ion absorbed by plants is changed to ammonium state before incorporating into amino acids. Animals procure their requirement of organic nitrogen from plant protein. They are first changed to amino acids to form animal proteins, nucleic acids etc.

Your Ad Here

During metabolism a anumber of nitrogenous waste products-urea, uric acid, NH₃ are released. Dead bodies also possess nitrogenous compounds. Wastage is acted upon by ammonifying organisms like bacillus species, actinomycetes and some fungi. They release NH₃ which escapes into atmosphere. Volcanic eruptions possess ammonia. Ammonia in soil is acted upon by nitrifying organisms. It is changed to nitrate state.

Your Ad Here

	Nitrosomonas		Notrocystis
NH3	--------->	Nitrite	--------->	Nitrate
	Nitrococcus		Nitrobacter, Penicillium	↓
				Plants

Some nitrate and ammonium salts are added to the soil as fertilizers. A part of nitrate is lost during leaching and precipitation and becomes constituent of rocks and is added again through weathering. Nitrates of soil are fixed by bacteria into gaseous form through denitrification (some denitrifying bacteria are Pseudomonas aeruginosa and Thiobacillus denitrificans).

	Home
Oxygen Cycle Nitrogen Cycle Water Hydrologic Cycle Phosphorus Cycle Sulphur Cycle and Minerals Flow of Energy