ISCI 1A24 Lecture Notes - Lecture 16: Oxygen Cycle, Nitrogen Fixation, Nitrogen Cycle
29 Sep 2016
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Document Summary
Oxygen is the 2nd most abundant substance in our atmosphere. It is a powerful electron acceptor, as shown above. Ozone is very important, formed by unique reactions that occur in the upper atmosphere. Nitrogen is the most abundant chemical in our atmosphere (but less abundant than oxygen on the planet), but is not useful to the biosphere in its gaseous form. Proteins are nitrogen based, and minerals are also partially made up of nitrogen. Bacteria drive the processes of nitrification (nitrogen fixation) and denitrification are done by bacteria in soil to convert nitrogen to and from its gaseous form. Legumes have symbiotic relationships with bacteria (in root nodules). The bacteria get food, and the plants get accessible nitrates in return. This can allow for the replenishing of nitrogen in soil. Phosphorus is not found in insoluble form different than nitrogen cycle. Sulfur is a component of proteins, important to climate and biological processes.
