A1.2.2.1 Continued…



Nitrogen is moved into a cell and converted into ammonia and amino acids.


Ammonification is part of the process of organic decomposition. Organic nitrogen is converted into ammonia, by organisms such as microorganisms, bacteria and fungi.

When this process occurs without the presence of oxygen, it is called anaerobic. Slightly different reactions occur and the process results in the production of amines.


Denitrification almost counterbalances nitrogen fixation. This is the process that converts nitrate to nitrous oxide and nitrogen gas back into the atmosphere. It is conducted by denitrifying bacteria.

Human impacts on the nitrogen cycle:

Human activities such as burning wood and fossil fuels can increase the amount of nitrogen in the atmosphere. Certain reactions can occur, which then form acid rain. Nitrous oxide is a greenhouse gas, meaning that it contributes to global warming.

Nitrogen based fertilisers are a major human impact upon the Nitrogen cycle. They may be washed off the oil (or leach through the soil) into watercourses.

Excess quantities of nitrogen in water may rapidly increase the growth of algae (Eutrophication). This in turn can reduce the amount of oxygen in the water that is available to water dwelling organisms, which will then die. Too much nitrogen may also make soil unsuitable for plant life.