Biology Reference
In-Depth Information
a continually changing internal and external context also depends on catalysts,
in this instance on their capacity for being regulated. Hofmeyr & Cornish-
Bowden (2000) developed their theory of metabolic supply-demand to describe
this aspect of autonomy.
The above logical analysis of the consequences of materiality and autonomy
has led inexorably to the need for specific catalysts that are functionally organised
in such a way that they form a closed loop of efficient causation. The rest of
this chapter explores what this type of functional organisation may look like
and how it is realised in living cells as we know them. First, however, we need
a way of formally representing a self-fabricating system as an organisation of
catalytic components.
4. FABRICATION AND THE LOGIC OF LIFE
What is fabrication? Are there basic principles underlying fabrication? Must a
fabricator be more 'complicated' than that which it fabricates? Can a fabrica-
tor fabricate itself? One would suppose that by now there would have been
developed, either by engineers, technologists or anybody that designs or makes
gadgets, a full-fledged theory of fabrication that answers such basic questions.
The theory of self-replicating automata developed by von Neumann (1966, 1951)
goes some way towards answering these questions, but other than that I have
not been able to find a theory of fabrication.
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Seen abstractly, fabrication is a process in which a material object is created
either by rearrangement of, or by taking away from, or by adding to an existing
object. Usually, one assumes that this process is accomplished by a fabricator,
which is itself a material object (and, of course, not necessarily alive). However,
one has to leave open the possibility that the fabrication process happens spon-
taneously without assistance from a fabricator. In keeping with my background
as (bio)chemist, I take my cue from chemistry (the epitome of a fabrication
world). Consider A, B, C and P to be either (i) single molecules in which all
the atoms are bonded covalently or (ii) assemblies of molecules that associate
through noncovalent forces (ionic and hydrogen bonds, Van der Waals forces,
hydrophobic interactions, etc.). One could consider as an example of the first
a single polypeptide and of the second an enzyme consisting of noncovalently
associated subunits, each consisting of a single polypeptide. A new molecule can
form from existing molecule(s) in a number of ways, shown in Fig. 2. Because
it is all too easy to forget that physical laws such as the conservation of mass
underlie all fabrication processes I depict them using both symbols and schematic
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Besides biology, nano-engineering is also a field from which such a theory could arise (Drexler, 1992;
Freitas Jr & Merkle, 2004).
