How do fish separate oxygen from H20 & consume it? Do they break
the water molecule and absorb the oxygen only? The answer to
this, I recon, is that they don't. They use molecular oxygen
(O2) dissolved in the water for respiration, where is acts as a
terminal electron acceptor, just as we use molecular oxygen in
the air for respiration. We can speak of the water as being
oxygenated. What is split in photosynthesis, where reducing
equivalents from water are used to reduce NADP+ (giving NADPH).
One of the great discoveries of biology, IMO, is that the oxygen
formed in green-plant photosynthesis comes from water, not CO2.
Tricarboxylic Acid Cycle (Krebs Cycle) Rant Despite claims to
the contrary, most infamously by Racker (1976, pp 28 - 29) and
Wieser (1980), but also by Madeira (1988) and Mego (1986) for
example, water is not split in the tricarboxylic acid cycle
(Krebs Cycle). Banfalvi (1991) also sails pretty close to the
wind on this one. That is, reducing equivalents from water are
not passed down the respi