Biology Reference
In-Depth Information
Environment
9
8
7
10
11
12
Cell Functions
=
1
2
3
DNA
RNA
Proteins
IDSs
6
5
4
Fig. 10.1 The Bhopalator 2011: a bionetwork version of the Bhopalator model of the living cell
(Sect.
2.11
)
. Not shown in the figure are the
biochemicals
that serve as the free energy source for
directed motions of biopolymers, the most fundamental characteristics of life at the cellular level
not included in the original version of the Bhopalator, represent the following
unidirectional interactions:
7
¼
RNA control over DNA (e.g., siRNA, microRNA),
8
¼
protein control over DNA (e.g., transcription factors),
9
¼
protein control over RNA (e.g., RNA-binding proteins),
10
¼
receptor-mediated input of environmental
information (e.g., hormones,
cytokines, morphogens), and
11
nonreceptor-mediated interactions with environment (e.g., mechanical pres-
sure, osmotic pressure, radiative damages)
Figure
10.1
provides a convenient
visual
summary of the complex molecular
interactions and their properties that underlie life on the cellular level. The
text
version of these interactions and properties is given below:
¼
1. The ultimate form of expression of genes is not proteins (i.e.,
equilibrons
)asis
identity hypothesis
in Sect.
10.2
.
2. IDSs exert feedback controls over DNA (Step 6), RNA (Step 5), and proteins
(Step 4).
3. IDSs are postulated to be the sole agent through which the cell affects its
environment as indicated by the unidirectional arrow 12 in Fig.
10.1
.This
postulate is an alternative expression of
the
IDS-cell
function identity
hypothesis
.
4. Environment can affect DNA in two ways - through (1) receptor-mediated
mechanisms (see Steps 10 and 9), and (2) nonreceptor-mediated mechanism
(see Steps 11 and 6).
