Cell Signaling and Communication - 1
Just as we communicate with other humans in a number of different ways, cells
communicate with other cells and with their external environment with a set of cell
signal mechanisms and process signal information in order to make appropriate
responses within the cellular environment.
Cellular communication is necessary to
coordinate the myriad activities needed for any organism (unicellular or
multicellular, prokaryote or eukaryote) to grow, develop and function.
organisms use the same kinds of cell signaling mechanisms affirming again the
uniformity of DNA for life processes.
Cells typically use chemical signals for communication, but electromagnetic signals
(light) and mechanical signals (pressure or touch) are not uncommon. Plants in
particular respond to a host of external environmental signals. Nerve cells of
animals are especially sensitive to stimuli (e.g., chemoreceptors,
mechanoreceptors, photoreceptors, thermoreceptors, nocireceptors (pain),
However, cell-to-cell communication is most often chemical,
and chemical communication within multicellular organisms, particularly in animals,
is the focus of this section.
To start our discussion, lets look at a few examples of cell signaling to give you an
idea of what we mean:
Cellular slime molds secrete chemicals that induce adjacent cells to aggregate
into a multicellular "slug" when growth conditions are unfavorable.
This slug can
disassemble, migrate or form a resistant "fruiting body" depending on the
Some myxobacteria aggregate to form a resistant colony, or fruiting body,
when their nutrients are diminished.
Nutrient deficient bacteria secrete a
chemical into their environment that attracts others.
Within the fruiting body,
the cells produce thickened walls, forming resistant spores that withstand the
Many protists and other unicellular organisms are similar in morphology.
is determined by genetic "mating types" and sexual reproduction requires
individuals of different mating types to recognize each other in non-visual ways.
Recognition is chemical.
One individual recognizes an appropriate mate by
secreting its chemical mating factor for which a compatible mate will have a
The compatible mate will secrete its mating factor, for which the
original cell has a receptor.
These signals bind to the respective membrane
receptors of the "mate" to trigger fusion of the two cells. Typically, once a
zygote is formed, meiosis occurs and the new generation's haploid cells are
50% will have one mating type, 50% the other.