The Nitrogen Cycle

Essay by he_who_owns_youHigh School, 10th gradeB-, October 2006

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78% of air is nitrogen (N2). Nitrogen is in DNA, protein, and other compounds. Like carbon, nitrogen passes along food chans and circulates between biotic and abiotic enviroments.

Most organisms can't use nitrogen in it's natural form. Plants can only use it in the form of nitrate (No3-)

The Nitrogen cycle has three pathways. Nitrification, Nitrogen fixation, and denitrification.

Nitrogen fixation occurs from lightning and bacteria.

1a) Nitrogen fixation by Lightning

The process of turning nitrogen into a usable substance. The energy from lightning reacts with oxygen in the air to make nitrate, which is disolved with water and it seeps into the soil. The plants use the nitrate to make an acid called amino acid. Animals that eat the plants take in the acid and use it as a protein.

b) Nitrogen fixation by Bacteria

Bacterias convert the nitrogen to ammonia. A nitrofiying bacteria called cyano bacteria changes the ammonia into nitrate.

Some bacterias found in soil produce nitrate through small lumps called nodules. Bacterium uses the plant for storage of usable nitrate which will then use them to make ammino acids.

Plants provide bacteria with sugar which is needed to make nitrate.

2) Nitrification

Ammonia will react with water and become ionized. Bacteria in the soil will break down the ammonia into Nitrite (No2) , another bacteria will then turn the nitrite into nitrate. The nitrate will then be dissolved by rain water or another source of water and absorbed by plants.

ammonia - ammonia(ionized) - nitrite - nitrate

3) Denitrification

Denitrifiying bacteria breaks down nitrate back into nitrite and then back into nitrogen gas which goes back into the atmosphere.

Denitrification results in balance among nitrates and nitrogen gases.

Denitrifiying bacterias don't require oxygen.

Nitrate - Nitrite - Nitrogen gases

Human Effects on the Nitrogen cycle...