Why Is the Cell So Complex? - Molecular Theory of the Living Cell - page 572

Table 17.1 Examples of the classification scheme based on the triple criteria of (1) energy
(1 ¼ equilibrial, 2 ¼ dissipative), (2) size (A ¼ microscopic, B ¼ mesoscopic, C ¼ macro-

scopic), and (3) viability (a ¼ living, b ¼ nonliving)

Energy
1. Equilibrium

2. Dissipative

Size (A) Micro (atoms,

molecules)

(a) Thermal fluctuations
of enzymes

(a) Enzyme catalysis

(b) Thermal motions
of molecules

(b) Electronic excited states,
vibrational excited states

(B) Meso (cells,
nanoparticles)

(a) Cell membrane (a) Membrane potentials,

chemotaxis, morphogenesis

(b) Brownian motions
of nanoparticles

(b) Bernard convection cells

(C) Macro (humans,
stars)

(a) Skeletons (a) Body motions, thinking

(b) Rocks, continents,
planets

(b) Belousov-Zhabotinsky
reaction, tornadoes, stars

involved are alive. Thus, according to this triple criteria scheme , there are a total of
12 distinct classes of physical entities that we can recognize in the Universe as
shown in Table 17.1 . For example, the morphology of rivers would belong to Class
2Cb, the moon to Class 1Cb, stars to Class 2Cb, the cell to Class 2Ba, etc. This way
of classifying physical entities is not free of ambiguities. In order for the cell to exist,
its dissipative structures must be supported by equilibrium structures at both the
micro- and mesoscopic levels. In other words, Class 2Aa structures cannot exist
alone but must be supported by Class 1Aa and 1Ba structures.
The living cell exhibits two broad categories of complexities - the structural
(i.e., Class 1Aa and 1Ba entities) and dynamic (i.e., Class 2Aa and 2Ba entities).
When trying to distinguish between equilibrons and dissipatons , it is important to
keep in mind that the distinction critically depends on the size of the time window
(TW) employed, that is, the time range (minutes, hours, days, years, etc.) within
which observations or measurements are made. For example, although entity A is
classified as an equilibron with a TW in the minutes range, A may appear as a
component of dissipation when the TW is increased to days, if the half-life (HL) of A
(i.e., the time it takes for A to undergo 50% of its maximal change) is in hours.
In other words, the concepts of equilibrons and dissipatons are not absolute
but relative to the size of the ratio, TW/HL. If TW/HL is greater than say 10 2 ,an
entity Amay appear as a dissipaton, but when TW/HL is one or less, Amay appear as
an equilibron. Thus, it may be justified to make the following general statement to be
referred to as the Principle of the Relativity of Equilibrons and Dissipatons (PRED):

The concepts of equilibrons and dissipatons are relative and depend on the magnitude of the
ratio of the time window over the half life of the physical entity under observation. (17.1)
It is interesting to point out that Heraclitus thought that everything changes
constantly (and hence is a dissipation in my idiom), while Parmenides thought the
opposite, namely, that the ultimate reality is unchanging and eternal (and hence is an