Richard Kondo wrote:>>>>>>>>>>>>>>>
So why can we measure currents, if the cytoplasm is electroneutral? Probably,
because the insertion of a microelectrode (nowadays, we use a patch clamp
electrode which seals to the membrane) into the cytoplasm slightly
violates electroneutrality. There would be a voltage difference between
the membrane and the electrode, but it would be extremely small, because
the conductivity of ionic solutions is very high. (just like a copper wire).
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Thank you, Richard, for your extremely interesting comment. I am citing only
a small part of your text as it seems to me that it gives a clue to
understanding the general problem. So the cytoplasm (or generally, a point
far enough from the membrane) is electroneutral and yet the MEASURED
potential does not differ from that at the membrane. In my opinion your
explanation is correct - we just have a "wire" effect. Still I think that
the REAL potential, defined as the work needed to move a positive test
charge from infinity to the point, is ZERO. There is an apparent difficulty
in this particular case as one may not be able to see the path from
infinity to the point, but this is not a serious objection. There are
analogous cases in which the membrane is flat so the path from infinity to
the point is open. In conclusion, as we go away from the membrane, all
three quantities - the charge density, the field and the potential, approach
zero. Do you agree?
Best regards,
Pentcho
