Biology Reference
In-Depth Information
Gánti uses several biochemical cycles to illustrate the ideas in the chemoton.
He begins with the citric acid cycle introduced above and initially de-emphasizes
the importance of new inputs of acetyl-CoA and instead emphasizes that
oxaloacetic acid and all other intermediates are regenerated by the cycle. He
represents this by the following formalism (Scheme 1)
18
:
Krebs
Oxaloacetic acid
Oxaloacetic acid
1
Scheme 1
To show that the nutrient material is entering the cycle and waste products
are leaving, he expands the formalism (Scheme 2):
Krebs
Oxaloacetic acid
+
CH
3
-CO
+
3H
2
O
Oxaloacetic acid
+
2CO
2
+
9H
1
Scheme 2
More abstractly, Gánti uses
A
for the components of the cycle,
X
for the
reactants entering the cycle, and
Y
for the reaction products (Scheme 3):
Krebs
A + X
1
A + Y
Scheme 3
For Gánti the citric acid cycle is only the starting point. He views living
systems as fundamentally growing systems and so turns to autocatalytic cycles
18
This formalism, as Griesemer & Szathmáry (forthcoming) discuss, was introduced by Gánti so as to draw
attention to the stoichiometric requirements of catalyzed reactions. This attention to the flow of matter through
the system by balancing each reaction is an important feature of Gánti's approach.
