These two processes are involved in the nitrogen cycle. I wonder why these two pathways need additional electrons !
Oxidation state of N in nitrite is +3 and N in ammonia is -3. Therefore, net change of electrons in annamox reaction is 0.
In the first step of nitrification (oxidation of ammonia to nitrite) there is no need in additional electrons. BUT there is "hidden" requirement of electrons to "prepare" oxygen for hydroxylation of ammonia. Ammonium monooxygenase does not use O from water for hydroxylamine formation it does use O from O2. For this it needs to bring O with zero oxidation state to O with -2 oxidation state. Here additional electrons are required. However, in general equation this is "hidden" by the usage O2 as electron acceptor.
What both processes require is so called reverse electron transfer: to bring electrons released at higher redox potential reaction into lower redox potential reaction. In both cases that are reactions of assimilation of CO2. That normally is achieved by ATP hydrolysis (or any other reactions) that brings up the proton motive force and makes energetically unfavorable reaction to occur.
I will be using oxidation states to estimate electron balance without considering the complex periplasmic and cytoplasmic enzyme process within the respective bacteria. Anammox reaction involves conversion of NO2- to N2 and NH4+ to N2. Oxidation states of NO2- is IV, NH4 is -III and N2 is zero. Therefore, NO2- to N2 will need 4e and NH4 to N2 will yield 3e. Therefore only 1 additional e is consumed from the above two combined reactions.
Nitrification is conversion of NH4 to NO3. Oxidation state for NO3 is V. Therefore the entire nitrification reaction should yield 8e. This pathway does not need electrons, it yields electrons.
Oxidation state of N in nitrite is +3 and N in ammonia is -3. Therefore, net change of electrons in annamox reaction is 0.
In the first step of nitrification (oxidation of ammonia to nitrite) there is no need in additional electrons. BUT there is "hidden" requirement of electrons to "prepare" oxygen for hydroxylation of ammonia. Ammonium monooxygenase does not use O from water for hydroxylamine formation it does use O from O2. For this it needs to bring O with zero oxidation state to O with -2 oxidation state. Here additional electrons are required. However, in general equation this is "hidden" by the usage O2 as electron acceptor.
What both processes require is so called reverse electron transfer: to bring electrons released at higher redox potential reaction into lower redox potential reaction. In both cases that are reactions of assimilation of CO2. That normally is achieved by ATP hydrolysis (or any other reactions) that brings up the proton motive force and makes energetically unfavorable reaction to occur.
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