Biology Reference
In-Depth Information
this Michaelis constant, and certainly the concentration of the product of the
reaction changes the (effective) K
m
, i.e.
1
P
K
p
K
m, apparent
=
K
m
ยท
+
(3)
All components of the same living cell may therewith affect the role the
enzyme plays in the cell's behaviour, including the components that are not yet
known . This pinpoints one of the arguments of holism, in that to understand
the role of one of the molecules in a system with the type of nonlinearities found
in cell biology, one must look at the whole. We do not think that one should
necessarily be able to look at the whole all the time, but certainly one should be
able to look at all the possible molecular factors that play a role. Until recently,
not all molecules of the living cell were known or even knowable, making it
impossible for biochemistry and molecular biology even to determine with cer-
tainty the role a molecule of choice might play in determining the nonlinear
behaviour of the living system, simply because unknown factors could well be
clouding any issue. Post-genomics is beginning to change this.
2.6. Lack of experimental accessibility
As emphasized by Carnap (1966) for physics, it is important that hypotheses
are tested under all relevant conditions and in terms of all relevant degrees of
freedom. In living systems, many factors may exert an influence and it should
therefore be mandatory that proposed mechanisms are tested by modulation of
all those factors individually. For as long as not all those factors were known,
it was difficult for biology to carry out these tests; the living system was not
accessible enough for such testing.
2.7. Lack of analysability
Because many factors are likely to be involved in the sustenance of the liv-
ing state, hypotheses concerning mechanisms are likely to be multifactorial.
Accordingly, many of these factors should be monitored simultaneously in tests.
Although quite a few factors can be measured individually by biochemistry and
molecular biology, until recently it was impossible to monitor many components
simultaneously.
Summarizing, we see a landscape where biochemistry and molecular biology
could extend neither to physics nor to organismal biology because of at least
these seven types of limitation. We shall now discuss recent changes in molecular
biology that would seem to do away with some of these limitations.
