Image: Sources of Energy and Oxidants on Earth
of the energy sources available to organisms on Earth are shown on the left,
with the most energy rich at the top and the least energy rich at the bottom.
On the right are shown the available oxidants for the burning of these
biological fuels. The fuels and
oxidants commonly used by the eukaryotes are glucose and oxygen, while those
available to the prokaryotes are HCOOH, CH2O, H2, H2S,
CH4, S0, Fe++, NH4+, MN++,
and CO2, SO4, FeOOH, NO2-/NH4+,
NO3-/NH4+, MnO2, NO3-/N2
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