Biology Reference
In-Depth Information
3.1.1 Belousov-Zhabotinsky Reaction-Diffusion System
The Belousov-Zhabotinsky (BZ) reaction was discovered by Russian chemist, B. P.
Belousov, in 1958 and later confirmed and extended by A. M. Zhabotinski
(Babloyantz 1986; Gribbins 2004, pp. 131-34). The spatial pattern of chemical
concentrations exhibited by the BZ reaction results from the chemical intermediates
formed during the oxidation of citrate or malonate by potassium bromate in acidic
medium in the presence of the redox pair, Ce
+3
/Ce
+4
, which acts as both a catalyst
and an indicator dye. Ce
+4
is yellow and Ce
+3
is colorless. The BZ reaction is
characterized by the organization of chemical concentrations in space and time
(e.g., oscillating concentrations). The spatial patterns of chemical concentrations
can evolve with time. “Patterns of chemical concentrations” is synonymous with
“chemical concentration gradients.” The organization of chemical concentration
gradients in space and time in the BZ reaction is driven by free energy-releasing (or
exergonic) chemical reactions. The BZ reaction belongs to the family of oxidation-
reduction reactions of organic molecules catalyzed by metal ions. The mechanism of
the BZ reaction has been worked out by R. Field, R. Noyes, and E. Koros in 1972 at
the University of Oregon in Eugene. The so-called FNK (Field, Noyes, and Koroso)
mechanism of the BZ reaction involves 15 chemical species and 10 reaction steps
(Leigh 2007). A condensed form of the FNK mechanism still capable of exhibiting
spatiotemporally organized chemical concentrations is known as the
Oregonato
r.
A simplified mathematical model of the BZ reaction was formulated in 1968 and is
known as the
Brusselator
(Babloyantz 1986; Gribbins 2004, pp. 132-34).
3.1.2
Intracellular Dissipative Structures (IDSs)
Living cells are formed from two classes of material entities that can be identified
with Prigogine's
equilibrium structures
(or
equilibrons
for brevity) and dissipative
structures (or
dissipatons
) (Sect.
3.1
). What distinguishes these two classes of
structures is that
equilibrons
remain and
dissipatons
disappear when cells run out
of free energy. Dissipatons are also theoretically related to the concept of
“attractors” of nonlinear dynamical systems (Scott 2005).
All of the cellular components that are
controlled
and
regulated
are dissipatons
referred to as intracellular dissipative structures (IDSs) (Ji 1985a, b, 2002b). One
clear example of IDSs is provided by the RNA trajectories of budding yeast
subjected to glucose-galactose shift that exhibit pathway- and function-dependent
regularities (Panel a in Fig.
12.2
), some of which were found to obey the blackbody
radiation-like equation (see Panels a through d in Fig.
12.25
). The main idea to be
suggested here is that IDSs constitute the immediate causes for all cell functions
(Ji 1985a, b, 2002b). In other words,
IDSs
and
cell functions
are synonymous:
IDSs constitute the internal (or endo) aspects and cell functions constitute the external
(or exo) aspects of the living cell.
(3.2)
