AP BIOLOGY

Detailed explanation-1: -For nitrogen to be available to make proteins, DNA, and other biologically important compounds, it must first be converted into a different chemical form. The process of converting N2 into biologically available nitrogen is called nitrogen fixation.

Detailed explanation-2: -Fixation. Nitrogen in its gaseous form (N2) can’t be used by most living things. (Plants for example, do not have the required enzymes to make use of atmospheric nitrogen.) It has to be converted or ‘fixed’ to a more usable form through a process called fixation.

Detailed explanation-3: -Nitrogen gas from the atmosphere is fixed into organic nitrogen by nitrogen-fixing bacteria. This organic nitrogen enters terrestrial food webs.

Detailed explanation-4: -Nitrogen is fixed, or combined, in nature as nitric oxide by lightning and ultraviolet rays, but more significant amounts of nitrogen are fixed as ammonia, nitrites, and nitrates by soil microorganisms. More than 90 percent of all nitrogen fixation is effected by them.

Detailed explanation-5: -All living things need nitrogen to build proteins and other important body chemicals. However, most organisms, including plants, animals and fungi, cannot get the nitrogen they need from the atmospheric supply. They can use only the nitrogen that is already in compound form.