The Control Mechanism
in the Communication Within Cells
The insulin hormone.
Different hormones have their own particular effects
on their target cells; this is necessary if the human
body is to function in an orderly way. For example,
the messages carried by insulin and glucagon-the hormones
that adjust the level of sugar in the blood-are completely
opposite in structure to one another. For this reason,
these two hormones stimulate different communication
pathways in the cell. The receptors that function like
a communications station inerrably find the communication
module to relay the message.
If a wrong choice were made at this stage, the communication
network would fail and the person may die. But the receptors
on the cell's membrane work like experts, ensuring that
communication continues without interruption.
How do receptors that are stimulated by different hormones
select without error the messenger proteins with which
they must unite? How do the receptors successfully perform
their functions without making a fatal error? Recent
scientific research has helped us to find the answer
to these questions. The flawless communication within
the cells comes from their perfect design.
Let us consider the SH2 module about which we know
most. This small piece of protein is composed of two
main parts. One section of SH2 is the part that attaches
firmly to the tail of the receptor. The second section
of SH2, the section that gives it its basic characteristic,
operates like a code reading device.
The number and arrangement of amino acids in the tail
section of the receptor forms the code of the message
being brought to the cell. This code is only deciphered
by a certain kind of SH2 module. It is this same module
that unites with it. Another section of this module
unites with a different module. In this way, a special
line of communication is established between the membrane
and the cell nucleus. In short, all these complicated
operations do not happen at random; they are organized
according to a definite system. This arrangement is
another demonstration that everything has been created
in a measured and harmonious way.
The communication system in cells is much more
highly advanced than the communication network
between the branches of an international company
with production and marketing centers throughout
Now, in order to observe an example
of this harmony, let us examine the communication mechanism
that goes into action to repair the area where a person
has cut his hand. In this situation, a messenger molecule
called "platelet derived growth factor" (PDGF) unites
with the receptor of the smooth muscle cell in the blood
vessel that has received the damage. As a result of
this union, the tail of the receptor inside the cell
binds to a protein called Grb2. Grb2 is a messenger
protein formed from the union of SH2 and SH3 particles;
in order to establish communication among the proteins,
it takes on the function of an adaptor. Next, Grb2 assimilates
a messenger protein called "sos" which is in the cytoplasm
that contains enzymes. Sos then activates another protein
named "ras." In this way, at the end of a number of
operations, it sends instructions to the relevant genes
in the cell. Then the cells begin to multiply in order
to heal the wound.46
Scientists make the following evaluation based on their
research: in the communication system of the cells are
mechanisms that automatically prevent a malfunction.
These mechanisms are the product of superb design much
more advanced than the control systems employed by modern
high technology. So it is that, ever since the creation
of human beings, hormones, receptors, adaptors, proteins
and microscopic elements have been operating in perfectly
It is impossible to conclude that such a complex order
has come to be by evolution. The complexity of this
system is extraordinary and more advanced than a communications
system established by an international company, with
branches, production and marketing centers all over
the world. Above all, it is not conscious, informed,
educated and intelligent human beings who operate this
wonderfully integrated communications web, but tiny
molecules too small for the eye to see. Certainly it
cannot be expected that molecules establish such a system
among themselves. The One Who established this system
and controls it is God.
Special Messengers in the Cells
Internet technology is one of the most important
developments in human history. But, the speed
and capacity of the information transfer provided
by the Internet is quite simple compared to the
transfer of information in cells.
If you asked your friends what was the most important
communications event of our time, "the Internet" would
most probably rank first. Then, ask them why they think
this. They will tell you that internet technology has
made it possible for a great amount of information to
be transmitted from one end of the world to the other
within a short time. Internet technology is one of the
most important developments in the history of humanity,
but it is also true that the speed and capacity of information
transmission afforded by the Internet is slow compared
to the transfer of information among cells.
The nerve cells in the brain cells (neurons) or eye
cells actually have the fastest known capacity for the
transfer of information.
In these cells are systems functioning
at every moment to make the transfer of information
fast and without error. The latest research on the communication
web of nerve cells has shown that some proteins in neuronal
pathways have an "incredibly large number of linker
domains."47 Therefore, these proteins
are able to hold groups of messenger proteins together
permanently. The very rapid communication in nerve cells
is the result of this special design.
As an example of the special proteins that have a role
in the communications mechanism in the world of cells,
we will consider PSD-95. This messenger protein is thought
to be an agent in the neurons related to learning.
PDZ is one of the various linker modules of
the PSD-95 protein. In the first picture, you
can see the structure of the PDZ module. In
the picture on the right, the red areas are
the PSD-95 protein.
In the linker modules of the PSD-95 protein are three
PDZ domains. The first of these attaches to the tail
of the receptor in the cytoplasm; the second controls
the ion channel in the membrane of the cell; the third
grasps the messenger proteins in the cytoplasm. In other
words, the linker modules in the structure of PSD-95
makes it possible for it to coordinate several elements
of communication at the same time.
This wonderful communication system is not limited
to the nerve cells; a similar system exists in our eyes.
You are reading this book due in large measure to the
rapid communication system in the cells in your eyes.
This marvelous mechanism is also found in the eyes of
animals. Research on fruit flies has demonstrated that
in this creature's compound eye containing many smaller
eyes, special communication modules exist. The operation
model of the special "InaD" messenger protein that causes
the transfer of visual messages from the eye to the
brain of a fruit fly is outlined below.
How did proteins establish such intelligent and particular
communication systems? And how is it that proteins have
constructed communication networks to respond immediately
to the different needs of 100 trillion cells? And again,
how did the wonderfully designed module system agree
among themselves and formulate plans to form complex
eye of a fruit fly contains many smaller eyes
and research has shown that there are special
communication modules within this mass of eyes.
Above you can see a simplified diagram of the
operation of the special communication protein
called InaD, which affects the transfer of visual
messages from the eye of a fruit fly to its brain.
The modular system in the world of cells can be compared
to the International Space Station. This station, built
on the modular system, is recognized as one of the greatest
engineering achievements in human history. No one can
claim that this space station came to be by the chance
combination of atoms, molecules, wind, lightening, or
solar energy. The fact is, this space vehicle was built
as a result of highly intricate engineering calculations,
based on a pool of knowledge built up over the years
by scientists from many countries.
|The nearest thing
to the modular system in the world of the cells
is the International Space Station that is still
being constructed according to a modular system.
Who made this communication system working inside cells
whose technology is so advanced those scientists cannot
completely unlock its secrets?
The messenger proteins and the wonderful
communication systems formed by them are created and
ordered by God, "He created all things" (Qur'an, 6:
101) and "directs the whole affair from heaven to Earth."
(Qur'an, 32: 5).
46 J.D. Scott, T. Pawson, "Cell
Communication," Scientific American, June 2000,
47 Scientific American, June 2000, p. 76