Sub 4: Nutrient Cycling Flashcards
what is carbon essential for?
as a component of carbohydrates, proteins and fats
what is nitrogen essential for?
element in nucleic acids and protein
what are the five steps of the nitrogen cycle?
nitrogen fixation, nitrification, assimilation, ammonification, denitrification
what is nitrogen fixation?
reduction of atmospheric nitrogen to ammonia
what is the enzyme that catalyses nitrogen fixation?
nitrogenase
what are the conditions of nitrogenase?
needs a lot of energy 16ATP per N2 molecule
completely inhibited by oxygen
what are the two main types of nitrogen fixing bacteria?
cyanobacteria and rhizobium
what are cyanobacteria and how do they create anaerobic conditions?
they are free-living but live as chains of cells and some form cysts which are impervious to oxygen creating anaerobic conditions for nitrogenase, other cells in the chain respire aerobically to produce the large amounts of ATP required
what are rhizobium?
form a mutualistic relationship with legume plants and live in the root nodules that the plant fills with leghaemoglobin which binds with oxygen creating anaerobic conditions necessary for nitrogenase function
oxygen is then slowly released for aerobic respiration so that the bacteria can produce large amounts of ATP required for nitrogenase
why is the rhizobium/legume plants described as mutualistic?
both organisms benefit
Rhizobium gain nutrients and protection from the legume
the legume gains a source of nitrogen - to make amino acids
what is nitrification?
the conversion of ammonia to nitrites to nitrates
what bacteria are involved in the conversion of ammonium to nitrite?
nitrosomonas and nitrococcus
what bacteria is involved in the conversion of nitrite to nitrate?
nitrobactor
is nitrification aerobe or anaerobic?
aerobic
what is assimilation?
the uptake of nitrogen or ammonia by primary producers and their incorporation into proteins and nucleic acids
