Biology Reference
In-Depth Information
Waste
Nutrient
A
2
X
Y
A
1
A
3
A
1
Metabolic
cycle
R
pV
n
V
1
A
4
Control
A
5
V
′
pV
n
pV
n
V
n
pV
n
T
′
T
?
Membrane
generation
T
T
m
Figure 4
Gánti's chemoton with the three subsystems labeled.
linked with each other such that as the metabolic system produced metabolites
it also produced membrane. This will work as long as the environment of the
system continues to provide the system exactly what it needs, regularly removes
its waste, and does nothing to interfere selectively with either the membrane or
the metabolic process.
Even slight variations in the environment may disrupt such a system. Imagine
the environment changed so that a new substance entered the system which would
react with existing metabolites, either breaking down the structure or build-
ing new additional structure. This would disrupt the delicate balance between
metabolism and membrane generation that Gánti relies on to enable chemo-
tons to reproduce. What this points to is the desirability of some procedures
for controlling operations within the system that are not directly tied to the
stoichiometry of the metabolic reactions themselves. Although stoichiometric
linkages between reactions are effective for insuring linkages between opera-
tions, they do not provide a means for varying the reactions independently. Such
independent control can only be achieved by a property not directly linked to
the critical stoichiometry of the system.
Griesemer and Szathmáry (forthcoming) provide an account of the stoichio-
metric freedom made possible with the information subsystem Gánti proposes.
If, instead of just one type of molecule being combined into the polymer, two or
more constitute the building block, then the polymer will exhibit both a composi-
tion of monomers in specific concentrations and a sequence. The concentrations,
