Living organisms and thermodynamics (Pentcho Valev)

RUMYM at BGEARN.ACAD.BG RUMYM at BGEARN.ACAD.BG
Thu Oct 16 09:32:49 EST 1997


Bill Tivol wrote:
Pentcho Valev wrote:                                                      <

> Please consider the following EQUILIBRIUM system:                       <

>                              low pH                                     <

>membrane-permeable-to-H+ only // impermeable-membrane-------------X------<

>                              high pH                                    <

>At equilibrium, a capacitor-like double layer is established where the   <
>membrane is permeable to H+ and, accordingly, a transmembrane electrical <
>potential opposes the H+ concentration gradient. This is a common and    <
>universally accepted picture. The essential problem is: Does this        <
>electrical potential reach the point X situated on the impermeable       <
>membrane, far enough from the permeable one?                             <
> In other words, is there, at                                            <
>the point X, a transmembrane electrical force which would oppose eventual<
>movement of H+ down the concentration gradient? If not (as I believe),   <
>an ATPsynthase placed at the point X could use this movement of H+ down  <
>the concentration gradient for ATP synthesis. As the "working" system    <
>is at equilibrium, this would be a violation of the second law.          <

    In any event, the 2nd law predicts that the chemical potential           <
for H+ should be the same throughout the system, so the combination of    <
potential & [] gradients at X would result in the ATP synthase not pro-   <
ducing ATP spontaniously.  I realize that it is just this prediction      <
which you are calling into question, and the only real test is to do      <
the experiment.  I have to believe, however, that some life-form would    <
have evolved this "free lunch" system in the last 3 billion years if      <
ATP could be synthesized this way.                                        <

The mechanism is not so extraordinary as it may seem. In fact, ATP can be
synthesized under equilibrium conditions even by today's enzyme - it has
been shown experimentally that the reaction ADP + P = ATP occurs in the
isolated moiety of the ATPsynthase and the ratio reactants/products is
about 1/1. The problem is that the synthesized ATP remains firmly fixed
to the enzyme, and some external agent must liberate it. This might have
happened within some ancient vesicles, and we are to find the possible
liberating agent. In other words, we should answer the question: As ATP
synthesis proper is a probable process but is restricted by the stable
bond between the reagents and the enzyme, what could have liberated ATP
at a time when the the specific membrane mechanisms (H+ extrusion) were
not yet developed? This question bothers not only me. Anthonie Muller
believes that periodic temperature changes might have done the job
(Prog. Biophys.molec.Biol. Vol.63, pp.193-231, 1995). His model obeys
the second law and has some experimental support.
   My model contradicts the second law and also can be verified
experimentally. The problem is that it acts like the face of Medusa the
Gorgon - people who see it get petrified, and so I have been asking them
for years just to measure the potential difference between the two ends of
a simple system, but to no avail. And this would be a verification of
both the second law and the conventional bioenergetic scheme|
   That everybody believes in the second law is normal. That nobody wants
to verify it is I do not know what.

Best regards,
Pentcho



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