Subcellular Systems - Molecular Theory of the Living Cell - page 316

the Wang-Gribskov model of the cell is the importance placed on RNA as the
primary memory relative to DNA viewed as the secondary memory, which may
seem to go against the DNA-centered paradigm in cell biology that has been
dominating the field of molecular biology since the discovery of the DNA double
helix in 1953. But this shift in emphasis from DNA to RNA embodied in the Wang-
Gribskov model of the cell is consistent with the emerging prominence of RNA not
only as the reliable indicator of biological complexity (Mattick 2004) but also as the
regulators of cell metabolism and functions (Mattick 2003, 2004; Storz 2002;
Zamore 2002). One of the reasons for the prominence of RNA over DNA in cell
biology may derive from the fact that RNA can serve as an enzyme but DNA
cannot. Thus RNA may have played an essential role in the origin of life because of
its ability to manipulate both energy and information and thus control organization
(see Fig. 4.8 ) .

11.2.7 Cell Architectonics

The study of the principles and theories of the architecture of the living cell may be
referred to as the cell architectonics . Just as a human architect designs a building to
achieve a set of functions desired by the occupant, the biological evolution has
designed the living cell to accomplish a set of functions that are essential for self-
reproduction or self-replication. It is important to recognize the fundamental
difference between artificial buildings and natural cells , however. The former is
other-designed and the latter is self-designed and self-organizing (Sect. 3.1 ).
If we designate the d iameter of a c ell as DC and the average d iameter of the
p articles inside the cell as DP, the n umber of p articles inside the c ell, NPC, can be
approximated as NPC

(DC/DP) 3 . Typically, a eukaryotic cell has a diameter of
10 5 m, and the average diameter of cell components (e.g., protons, oxygen, water,
metal ions, metabolites, proteins, RNAs, and DNA) can be estimated to be 10 9 m,
leading to 10 12 as the approximate total number of particles inside the cell. These
particles are not randomly distributed inside the cell but organized in space and time
to accomplish a set of functions that are beyond individual component particles.
In other words, to produce the properties essential for cell survival that are beyond
the capabilities of the components of the cell, these components must be organized
into higher-order structures according to the principle referred to as the Principle of
Emergent Properties (PEP) (Ji 1991). PEP states that:
Whenever a complex system S is constructed out of n sub-systems, s 1 ,s 2 ,s 3 ,

¼

... ,s n ,

according to a set R of m rules, r 1 ,r 2 ,r 3 , ... ,r m , then a set P of k properties, p 1 ,p 2 ,p 3 ,

,p k can emerge that is not found in less complex systems composed of any subset of S.
(11.13)
To organize the large number (~10 12 ) of particles inside the cell, the following
two requirements must be met.

...