Biomedical Engineering Reference
In-Depth Information
Figure 1
.
Hierarchical levels of organization in complex living organisms
. At each level of
the hierarchy, new entities and level-specific rules that govern their behavior emerge from the
interactions of the entities of the lower level. Thus, there is no "scale-invariance" as in fractals.
Here we focus on the "emergence" at the cellular and tissue levels of the characteristic me-
chanical properties (left) and features of cell fate behavior (right).
cyclin D; this then would lead to the phosphorylation and inactivation of the
cell-cycle inhibitor protein Rb, which, in turn, would result in the induction of
proteins involved in DNA replication (56). Although we are used to present this
type of Rube Goldberg machine-like mechanism of a molecular process in a
living cell as if it were explanatory, the reality is that such mechanistic represen-
tations are essentially descriptive. All we do is describe a chain of events at a
lower (molecular) level than the one used to make our initial observation (cell or
