Martin Cann asked:
>> I'm afraid I haven't had much luck in the literature with this one.
>> Do the CO2/HCO3 and HPO4/H2PO4 intracellular buffer systems cross talk by
>any known mechanism? For example does one modulate transport systems for
>the other? What are their relative contributions to intracellular
>buffering? What are the consequences for the cell on perturbing one, e.g.
>CO2/HCO3 balance, on the other?
>> I probably haven't explained myself well, having only just read what a
>Henderson-Hasselbach equation is!
>> Any advice or recommended references would be much appreciated
Petr's response is fine as far as it goes, but I have a suspicion that the
question was at a more basic level ("having only just read what a
Henderson-Hasselbach equation is!") and so maybe a more elementary answer
is needed.
If I understand correctly the question "Do the CO2/HCO3 and HPO4/H2PO4
intracellular buffer systems cross talk by any known mechanism?" this is
asking if two buffer systems mixed together in the same compartment must
have the same pH, and the answer is yes, because any protons released by
HCO3 can be taken up by HPO4 and vice versa. In a homogeneous solution,
therefore, there is only one proton concentration and hence only one pH.
The same applies to all other components at a system at equilibrium, i.e.
there is only one concentration of calcium ions, only one concentration of
any given ionic state of phosphate, etc. In brief, what Petr is referring
to is the difficulty (in complicated cases) of solving the equations so as
to give the same concentrations of all the species.
Incidentally, the chap's name was Hasselbalch, though the misspelling
without the second l is very common (even in some textbooks).
Athel
--
Athel Cornish-Bowden athel at ibsm.cnrs-mrs.frhttp://ir2lcb.cnrs-mrs.fr/~athel/homepage.htm
Phone: + 33 491 16 41 38; fax: + 33 491 16 45 78
CNRS-BIP, B.P. 71, 13402 Marseille Cedex 20, France
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