Scientists who study biogeochemical cycles often use the term fixation to describe converting an element from gaseous form in the atmosphere to solid form in the biosphere. For example, in the nitrogen cycle, bacteria are said to fix nitrogen by converting N2 gas into nitrates and nitrites in the soil that are later used to make organic macromolecules such as proteins and nucleic acids. There are many processes involved in cycling carbon, but only one is able to fix carbon from its gaseous form in the atmosphere to solid form in the biosphere. Which process performs carbon fixation