DNAunion: Part 2 of 2 of another response to a post by David Bowman.
>>>David Bowman: Similarly, with biological systems. If you take parts of
them out of the system, they behave differently in a different environment
than when they are left in the integrated system. The way they behave in the
integrated system is "downhill" as the 2nd law constrains the system's
overall behavior. The *different* way they behave when isolated from the
other biological structures is also "downhill" since the different
environmental conditions redefine just what it means to *be* "downhill" in
the different context. In neither case is the 2nd law "overcome".
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DNAunion: Agreed: the overall context/environment/set of conditions
determines whether an individual process can occur *when coupled to another
process as part of an integrated system*. That is, the overall system can
determine the *behavior* of the individual components, but I still believe it
is valid to state that the individual tendencies persist throughout.
In mitochondria of extant cells, ATP will not form from ADP and inorganic
phosphate. That is an uphill, non-spontaneous, thermodynamically disallowed
process. But yet it does occur (in a sense, at least). That is, once you
throw in excited electrons falling down complex electron transport chains,
transmembrane proton gradients, proton-motive force moving protons through an
ATPase, and rotation of the slotted "merry-go-round" in ATPase, then yeah, it
can happen. But even so, it is still scientifically accurate to say -
before, during, and after considering the mechanisms involved - that the
reaction ADP + inorganic phosphate -> ATP is an uphill, non-spontaneous
process: even though it happens in a roundabout way. To make it spontaneous,
one would need to reformulate the reaction to something like ADP + inorganic
phosphate + PMF + ATPase -> ATP. But note that establishing a PMF
(proton-motive force) is a thermodynamically uphill process itself, as it
requires pumping protons (hydrogen ions) against an existing gradient. And
also the synthesis of the ATPase itself is an uphill process, requiring
transcription and translation.
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>>>David Bowman: Back to the teeter-totter analogy. What it *means* to be
"downhill" in a problem that is driven by gravitational forces, is to move in
such a manner as to decrease the total gravitational potential energy of the
system *no matter* how many teeter-totters have frozen confections on them
that are interactively automatically dumped from one basket to another.
Whatever the system does *is* "downhill". Certainly, if various subparts of
the system are isolated from the interacting system then their behavior under
the influence of the Earth's gravity is expected to change according to the
circumstances they find themselves in. But however they end up behaving, in
any of those various circumstances, it is in a way that reduces the total
gravitational potential energy of the subsystem at hand and is thus
"downhill" behavior. In one case a particular end of a teeter-board may go
up, and under some changed circumstances it may go down. But whatever it
does, the system of which it is a part will decrease its total gravitational
potential energy, and the system's operation will be "downhill" in its
gravitational potential energy.
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DNAunion: Agreed. But why do you feel uncomfortable in my using the term
overcome in relation to an instance in which the influence that the tendency
of one component, B, imposes on another component, A, is great enough that it
causes A's behavior to change from its natural tendency itself?
*****************
>>>David Bowman: Back to thermodynamics. *Whichever* way a thermodynamic
system spontaneously behaves, it is found to be thermodynamically "downhill"
in that its behavior increases the net total entropy of all the relevant
interacting parts of the system (where the surroundings are to also count as
part of the system if they are in interaction with the rest of the system in
any significant way). Just because a composite process involves parts of the
system decreasing in entropy and other parts coupled to them increasing in
entropy is no indication of the second law being overcome, since any given
part per se doesn't even *have* a prior "tendency" apart from a particular
specification of how it is to be in interaction with other parts of the
system & surroundings.
****************
DNAunion: I disagree with the statement that the individual parts don't even
have a tendency except from that determined by the system in which they are
found. Let me use a simple example from the see-saw analogy.
There is a 10-lb bag of sugar in each of the baskets, such that the
teeter-totter is perfectly balanced. This is how I perceive our talking past
each other.
DAVID: The bag of sugar on the right has a tendency to remain motionless,
elevated above the ground, as it is part of a composite system. It has no
individual tendency: it's tendency is determined by the total system and that
tendency changes depending on the system's state, or even what system it is
placed in.
DNAUNION: The bag of sugar on the right has a natural tendency to move
towards the ground because of gravity - this is not its behavior because it
is part of a composite system. The bag of sugar itself does have a tendency
independent of the composite system. It's behavior differs from its tendency
because it is part of a composite system, and its behavior changes depending
of the system's state, or even what system it is placed in: but its tendency
would remain the same.
****************
>>>David Bowman: It is certainly true that biological processes *are*
multiple orders of magnitude more complicated that a process as cooling tea,
but as far as the relevance of the 2nd law is concerned, *it doesn't matter*.
In either case, when a process happens, *that's* it tendency, in that
particular circumstance. When it doesn't happen in some other circumstance,
then *that's* it tendency in the modified circumstance.
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DNAunion: Again, I think discrepancies arise between what I would say and
what you say here because:
(1) You refer to "process", singular, but are discussing an aggregate of
multiple processes.
(2) You are using the word tendency as I do behavior.
"when a process happens, *that's* it tendency, in that particular
circumstance."
I don't agree with the statement as stated. But I do agree with the
following two modified versions:
(1) "when [an aggregate] process happens, *that's* its tendency, in that
particular circumstance."
(2) "when a process happens, *that's* its [behavior], in that particular
circumstance."
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