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Why is nitrogen essential to life?
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Colorful diagram of the nitrogen cycle showing how nitrogen moves through the atmosphere, biosphere, and soil. It illustrates natural processes like nitrogen fixation, assimilation, ammonification, nitrification, and denitrification, as well as human activities such as fertilizer use and industrial emissions, with arrows and labels connecting elements like plants, animals, bacteria, and factories.
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Colorful diagram of the nitrogen cycle showing how nitrogen moves through the atmosphere, biosphere, and soil. It illustrates natural processes like nitrogen fixation, assimilation, ammonification, nitrification, and denitrification, as well as human activities such as fertilizer use and industrial emissions, with arrows and labels connecting elements like plants, animals, bacteria, and factories.
Nitrogen cycle Diatomic nitrogen gas is transformed into ammonium, nitrate, and nitrite compounds in the nitrogen cycle.

Why is nitrogen essential to life?

Written by
Kara Rogers
Kara Rogers is the senior editor of biomedical sciences at EncyclopƦdia Britannica, where she oversees a range of content from medicine and genetics to microorganisms. She joined Britannica in 2006 and...
Kara Rogers
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Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Britannica Editors
History

Nitrogen is fundamental to life because it is needed to make DNA and RNA, which carry genetic information, and amino acids, which form proteinsā€”all of which are essential to the composition of living organisms. Nitrogen is also a core component of chlorophyll, which absorbs energy from light in photosynthetic organisms, and adenosine triphosphate (ATP), the primary energy-carrying molecule found in the cells of plants and animals.

Earth is enveloped by an atmosphere that consists of about 78 percent nitrogen gas (N2). The vast majority of living organisms, however, are not able to use nitrogen in its gaseous form. To render this form usable, it must undergo nitrogen fixation, wherein the relatively inert gas is combined chemically with other elements to form more-reactive nitrogen compounds such as ammonia, nitrates, or nitrites. This process is carried out by certain bacteria and archaea. Ammonia and nitrates are absorbed by plants. Animals then obtain nitrogen by consuming plants or other organisms. The circulation of nitrogen in various forms through nature is known as the nitrogen cycle.

Kara Rogers