Biology Reference
In-Depth Information
4
How can we understand metabolism?
David A. Fell
SUMMARY
Metabolism is used as an example of a complex biological system where the
explanations that are given for how the properties and activities of the compo-
nents account for function at the system level have been changing. It is argued
that the difficulties in arriving at satisfactory explanations that contribute to
understanding arise because biological systems are the result of evolution. One
issue is that the system functions attributed to the components are not known
a priori
but are biological hypotheses, and errors in explanations in metabolism
have arisen through incorrect assumptions about function. Another issue is that
the study of knock-out mutants with no overt phenotypic differences from the
wild-type shows that some gene products may confer a significant selective
advantage, but their contribution to functionally relevant properties may be too
small to be discernable given the usual degree of variability in biological experi-
mentation. Lastly, the concept that each component makes a discrete and identi-
fiable contribution to system function may be true of human artefacts constructed
from discrete components, usually with intermediate levels of organisation such
as modules, but need not be true of evolved systems. If the functional char-
acteristics of biological systems generally arise from the interactions of many
components, with each component making small, but not critical, contributions
to various aspects of the overall function, then such systems may be amenable
to simulation, given the properties of the components and their interactions, but
the models may not be reducible to simpler levels of explanation.
