Just pondering an
example of entropic flow
De: Louis Agnew <mesroqilar@ameritech.net>
Para: ECOL-ECON
<Ecol-Econ@csf.colorado.edu>
Asunto: Entropy
Fecha: Domingo, 04
de Marzo de 2001 02:05 p.m.
<Glucose>--->
(Citric acid cycle)----> ATP ---->{Enzyme}---->
ADP ---->
(Citric
acid cycle)
[ATP = adenosine triphosphate, ADP = adenosine
diphosphate]
In this example from biochemistry, a 'disorder' aspect of entropy change
is represented by the geometric/geographic change in configuration between the
ATP and the ADP molecules. While the ATP molecule is recognized by the Enzyme -
protein, allowing it to retrieve the energy stored within, the ADP molecule is
not recognized. With respect to the 'needs' of the enzyme, the ADP molecule is
disordered. In order to recover the order, the ADP returns to the citric acid
cycle which dissembles a glucose molecule stepwise and transfers the energy
obtained by this process to the ADP, converting it back to ATP. Entropy is in
fact a reversible quantity, however, it is a measure of
the difference in energy content of a constant or specified system undergoing a
change in phase at a constant temperature. For instance, entropy is measured by
the change in energy that a solid undergoes at its melting point when it
changes to a liquid, dS = dH/T.
In the example, the ATP changes to ADP + phosphate, which results in two
molecules each able to move independently, and motion is a function of the energetics of a molecule. An increase in the capacity for
motion in a system translates as an increase in kinetic energy of the system,
but a lower potential energy of the system. Entropy reflects the increase in
kinetic energy of the system (two molecules bouncing around instead of one). It
requires the physical energetic quantity known as 'work' to convert the kinetic
energy of two molecules back into the potential energy contained by one. In the
citric acid cycle, the potential energy is initially obtained by dismantling a
glucose molecule into the fundamental parts of water and carbon dioxide. This
potential is transfered by enzymes within the citric
acid cycle to recombine the ADP and phosphate molecules to provide the
potential energy necessary for intracellular work.
In a normal, complete, citric acid cycle, several molecules of ADP are
converted to ATP, its been about 15 years, but I
remember the number as being over 20.
Interestingly, the various steps in the citric acid cycle occur at
differential rates, as is typical of all chemical processes. As a consequence,
if there is a sudden demand by an organism for energy, there is a shift in the
ratio of ADP to ATP within the body and the citric acid cycle is sped up. When
this happens, the slower steps in the cycle cause a buildup of intermediate
products and leads to shortcuts, such as lactic acid production, which is a
sort of pollution in the organism that can lead to its debilitation.
Relating
this to economics (I still have to read Nicholas Georgescu-Roegen..) It would appear that the faster an economy is driven, or
the greater the demand,
the greater the buildup of intermediates. Intermediates can be interpreted as
pollution and other externalities that are being neglected by focusing on
maximizing the rate or efficiency of the process. All rate limiting processes,
such as are required for sustainable use of agricultural or silvicultural
soils, watersheds, recycling or reprocessing of materials from the consumption
and production waste streams (the incomplete use of which represent a deficit
of work, even if a loss of potential), and careful consideration of our urban
infrastructural function, have aspects that are discounted to the future, which
would be less deleterious overall, if addressed at the opportune time such as
the present. These things, like the production of lactic acid in the citric
acid cycle represent wastes that can be metabolized in the future, but are not
energy efficient. Lactic acid in the body normally becomes a waste product that
the liver has to neutralize.
The
availability of a source of energy and an over zealous determination to 'grow'
produces an unsustainable demand on the social economy itself, such that much
potential is lost as a consequence. The material/energy demand is represented
by the ADP (debt) and the supply by the ATP material wealth). As long as there
is a fuel source to convert the ADP (debt) to ATP (material wealth) via the
'work' (production/labor) of the 'citric acid cycle' (Capital?), the economy
functions, but as the ADP (debt) builds up past the equilibrium level, there is
the consequent loss of complete metabolism resulting in the inefficiencies
characterized above. The inefficiencies are attributed to capital, but in fact
are a consequence of the demand to 'grow' that result in increased 'debt'.
Increased 'debt' requires 'capital' to enhance 'throughput' rates, resulting in
the shunting past, or neglect of, rate limiting processes.
The cure
is, as Daly (Fredrick Soddy) suggests, to eliminate
the abnormal burden on material wealth that 'growth' represents. All viable
species on earth have a limit to the size to which they will grow, even huge
species like whales, elephants or redwood trees approach a limit. There is no
precedent in nature for a biophysical or genetic dictate that predetermines the
absence of a limit to growth for the human social "leviathan". There
is, of course the apparent situation, that since we are culturally determined
and not biologically determined at this stage, the cultural form lacks the
necessary information to establish a 'natural' limit, leaving the question of
size open to conscious consideration. What then do we do to convert the optimum
"scale" into a subconscious process? (Rather than metabolizing all
its fuel, a tree converts glucose molecules into cellulose = wood. It grows
vertically, but its footprint on the earth hardly grows at all.)
The
insights are from reading Herman Daly's "Beyond Growth", 1996. The
biochemical analogy seemed apt. Hope i wasn't too
impetuous.
Byfhel,
Louis Agnew