Nitrogen is an important element that is used by living things. During the nitrogen cycle, nitrogen moves from the air to the soil, to living things, and back into the air.
Nitrogen in the air can't be readily used by living things. Bacteria that live on the roots of plants combine nitrogen in the air with other compounds. When nitrogen is combined with other compounds, plants are able to use it in order to produce proteins and other compounds.
Plants need nitrogen for the process of photosynthesis. Photosynthesis occurs when plants use absorbed light energy, water, and carbon dioxide to produce sugar and oxygen. Plants use nitrogen in pigments that help them absorb sunlight. Without nitrogen, plants could not create their own energy and the organisms on earth would lack food sources.
Image: Bacteria found on the roots of pea plants are able to combine nitrogen with other compounds in order to make it available to living things.