1, The nitrogenase complex in certain bacteria(( diazotrophs,;圆氮生勒 catalyzes the conversion of 6.20 sThe nitrogen in amino acids, purines, pyrimidines and other biomolecules ultimately comes from atmospheric nitrogen Cyanobacteria(蓝藻细菌 瘤菌, symbiont)cm/蔺 photosynthetic) and rhizobia(报 ix N, into nha The reduction of N, to NH, is thermodynamically favorable =N2+6e96H2NH31G0=-33.5kJ/mol But kinetically unfavorable: the bond energy for the triple bond in N, is 942 kJ/mol1. The nitrogenase complex in certain bacteria (diazotrophs,固氮生物) catalyzes the conversion of N2 to NH3 • The nitrogen in amino acids, purines, pyrimidines and other biomolecules ultimately comes from atmospheric nitrogen. • Cyanobacteria (蓝藻细菌, photosynthetic) and rhizobia (根 瘤菌, symbiont) can fix N2 into NH3 . • The reduction of N2 to NH3 is thermodynamically favorable : • N2 + 6e- + 6H+ 2NH3 G` o = -33.5kJ/mol • But kinetically unfavorable: the bond energy for the triple bond in N2 is 942 kJ/mol