Control Systems in the Living World - Building the Most Complex Structure on Earth - page 3

Metabolism
In performing their vital functions, living systems obtain energy by breaking down
nutrients, depleting their reserves of matter and free energy (catabolism). In order
to maintain their structure and function, living systems have to compensate for the
loss by synthesizing the lost components through the nutrients they take in with food
(anabolism). The equilibrium between the catabolism and anabolism in living sys-
tems represents their normal metabolism, which enables them to maintain a state of
dynamic material and energetic equilibrium.
Since the seventeenth century, metabolism has been considered a defining prop-
erty of living systems (viruses are metabolic parasites, and it is the host cell that goes
astray to produce its own killers). The maintenance of the structure and functions of
the cell require spatiotemporal coordination of a multitude of anabolic and catabolic
reactions occurring in the living cell. But the maintenance of the naturally erod-
ing cell structure requires that the cell somehow “knows” or has information on the
structure to be maintained and does the species-specific work at the right places and
at the right times within the cell's nanospace.
How does the cell accomplish this? If metabolism is understood to be the work
that the cell does to retain its structural identity, then how does the cell get the infor-
mation on the changes occurring in the system, how does it detect the deviations
from the norm, and, finally, how does it generate instructions to restore the normal
structure and send them to the changed structures? But if the living cell is not con-
trolled by external forces, as is clearly the case, metabolism implies the presence of a
built-in control system.
Control Systems Are Prerequisites of Living Systems
A cell is a supercomplex microscopic structure that performs thousands of reactions
coordinated perfectly in space and time every moment, and from the perspective of
physics, it is clearly an improbable construction. Nevertheless, it survives and per-
petuates its structure via reproduction. Theoretically, there are two alternative ways
that the living cell might accomplish this marvel of nature's biotechnology; all these
reactions are spontaneously coordinated, or, alternatively, the cell has evolved a con-
trol system to coordinate that myriad of chemical reactions within the cell.
The first possibility, that thousands of spatiotemporally precisely coordinated
biochemical reactions within the cell can spontaneously occur, seems next to impos-
sible. Emergence is a descriptive term that does not explain or help us explain any-
thing. The same can be said of self-regulation. Loose as they are, these terms only
avoid the questions on how cell structures arise and are maintained.
The alternative explanation of the phenomenon is that the wonderful spatiotem-
poral coordination of many thousands of chemical reactions occurring in a cell,
and many more in a multicellular organism, are controlled by a specialized system.
Human experience shows that even the simplest artificial devices or machines cannot
function without control systems involving continued human supervision and regula-
tion of material and energetic supply or built-in control systems.