Chapter 18Nitrogen Metabolism
Chapter 18 Nitrogen Metabolism
OxidationNitrogen CycleNitrogenstate-N-containing biological molecules-3NH,NH,:Ammonia,ammonium·Amino acidsion-2H,N-NH,HydrazineNucleotides-1NH,OHHydroxylamine: Cofactors (biotin)。N,NitrogenMany oxidation statesN,O+1NitrousoxideNO+2Nitricoxide. N2, N,O, NO, HNO2,NH3+3HNO,NO,Nitrous acid,? More than any other major elementnitriteion+4NO,NitrogenWhere can we get it?dioxide+5HNO, NO,Nitric acid,: about 78% of air is N2nitrateion+6Dependence on prokaryotes [prau'keript]· Cycle would not exist without bacteria and archaea
Nitrogen Cycle N-containing biological molecules • Amino acids • Nucleotides • Cofactors (biotin) Many oxidation states • N2, N2O, NO, HNO2,NH3 • More than any other major element Where can we get it? • about 78% of air is N2 Dependence on prokaryotes • Cycle would not exist without bacteria and archaea [prəʊˈkærɪɒt]
Nitrogen CycleFixing nitrogen (N2)·Essential for convertingN intousable chemicalform>Nonbiologicalprocesses(Lighting, Industry, combustion)
Nitrogen Cycle Fixing nitrogen (N2) • Essential for converting N into usable chemical form Nonbiological processes (Lighting, Industry, combustion)
Molybdenum/ma'libdanam/Nitrogen CycleFixing nitrogen (N2)Mo>Biologically/.dal.a'zau.trpf/. by microbes: diazotrophs (azote = nitrogen).CatalyzedbynitrogenaseVMetalloprotein:Fe-Sclusters,Fe-MocofactorsVSensitivetoO2:oxidizesFe-ScofactorsN,+8H++8e-+16ATP+16H0←→2NH,+H,+16ADP+16PLReadily becomes NH: (oK-9)
Nitrogen Cycle Fixing nitrogen (N2) Biologically /ˌdaɪ.əˈzəʊ.trɒf/ • by microbes: diazotrophs (azote = nitrogen) • Catalyzed by nitrogenase Metalloprotein: Fe-S clusters, Fe-Mo cofactors Sensitive to O2: oxidizes Fe-S cofactors • Molybdenum /məˈlɪbdənəm/
Nitrogen CyclenitrogendenitrificationfixationnitrogenaseWhere else can we get NH +?>Nitrates and nitritesNONHNitrateOccur naturally in water and soils>Reduction of NO3nitritenitratereductasereductase(nitrate) to NO2- (nitrite)nitrificationnitrificationNO;thentoammoniaNitrite>Carried out by plants, fungi, bacteria
Nitrogen Cycle Where else can we get NH4 +? Nitrates and nitrites Occur naturally in water and soils Reduction of NO3 _ (nitrate) to NO2 _ (nitrite) then to ammonia Carried out by plants, fungi, bacteria