[Captain Kwok]

Originally posted by Imperator Fyron:
How exactly would Ammonia, Methane or Sulfur Dioxide be used to get energy for complex organisms (not monerans, not protista, not any other forms of microscopic life)?

They would generally replace O2 in some sort of Version of the electron transport chain, which drives the production of ATP, the major energy carrier in the cell. Instead of O2 being the final electron acceptor to make H2O, one of the other compounds like SO4- (to H2SO4) would be. I suppose if there was lots and lots of the substance available in the alien cell, it might be able to produce enough energy. The problem is that the reduction potential is less than most of the energy carriers in the cell, so it needs to use more energy to get things started.

Some of the substances mentioned before work better as electron donors than acceptors, like ammonium, NH4+. For example, we use H2O as our electron donor for ATP synth, but on a planet with abundant NH4+, it might be possible for more complex organisms to use it the same way that nitrifying bateria do on Earth, but that still requires moderate levels of O2. However, it's just not energetic enough to be effective. But... H2 as an electron donor is fairly energy rich and might be able to form some sort of pathway, but I'm not so sure about the plausability of that.

[ February 20, 2003, 05:43: Message edited by: Captain Kwok ]