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.



Louis Agnew


Ing. Federico G. Salazar