Clas Blomberg - Physics of life-Elsevier Science (2007)

146 Part IV. Going further with thermodynamics
If there is no control and all developments are possible, it may develop into the most disordered
state of highest entropy, which simply can be defined as a collection of states where we do
not see any signs of order. From the low-/high-level descriptions, the “most disordered state
of highest entropy” corresponds to a dominating part of all possible realisations of low-level
distributions; equilibrium from the low-level description does not mean a particular state
but rather almost all possible low-level states that are consistent with the basic rules of the
system: the total energy, the fixed number of particles, the rules of the letters in the monkey
library, the particular cards in the card mixing.
There are several reasons why systems do not necessarily go to maximum entropy. Some
pathways for development can be more rapid than others and they may lead to states where
the system is caught up for long times in some kind of kinetic stationarity. This is particularly
apparent when chemical reactions play a basic role, as is the case for most of biological
processes at cell or molecular level. There are clearly defined equilibrium conditions for
chemical reactions and if all paths are opened (as it might be at high temperatures), then all
reactions can take place and one can get to final states with the most probable distribution of
various substances. However, at normal temperatures, which mean normal temperatures at
earth and of all biological systems, few chemical reactions appear spontaneously with any
significant speed. Gases can appear in the atmosphere without reacting, while some enhanced
temperature by any kind of ignition can cause an explosion. A proposed scenario for the
production of important organic compounds such as amino acids at the early earth is that they
were formed by particular processes in the atmosphere, triggered by ignition by electric
discharges of strong UV radiation and then dissolved in the seas where they could remain
stable without disintegration for millions of years if the temperature was not too warm. This
certainly represents such a kinetic stationarity and not a thermodynamic equilibrium.
Catalysis provides important paths for the development along certain paths by allowing
certain processes while others are prevented by too slow reaction rates. This allows the
production of certain compounds and also the building up of macromolecules. There is no conflict
with the second law here; as most pathways are closed, the development is restricted and
a complete disorder is prevented, but there is no question of building up order from disorder.
§ 16 STATISTICAL THERMODYNAMICS MODELS
16A
Magnetic analogies and molecule conformations
It has been very useful for much of the progress in science and physics to use analogies,
to take over ideas and formalisms originally developed for one kind of system and problem
to quite different questions. This should not mean that the systems are similar but rather that
one can make analogies between the concepts in the different systems and that a mathematical
formalism developed for one system to a large extent can be taken over to another type of
problems. Comparisons between the systems treated in that way can lead to new insight. This
can mean powerful methods for new type of problems. We will see some examples of that in
this book. One of the most far-reaching concerns of stochastic resonance is where a primary