Water vapor is in equilibrium with the air, that's natural law ... how much water depends on temperature alone ... roughly 7% per ºC at normal surface temperatures ...
I don't know much about the Kreb's Cycle, I'm told a massive dose of penicillin will take care of it ... but I do know this cycle consumes ATP, and spits out ADP ... which in turn is consumed by respiration, and ATP is spit out again ... what's usually called the energy cycle ...
Breath on a cold mirror ... or get some houseplants ... water is a powerful GHG ... but it also condenses ...