Chapter 11 - Chapter 11 Cell Communication Chapter 11 Cell...

Chapter 11 - Cell Communication
Chapter 11 Cell Communication
Lecture Outline
Overview: The Cellular Internet
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Cell-to-cell communication is absolutely essential for multicellular organisms.
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Cells must communicate to coordinate their activities.
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Communication between cells is also important for many unicellular organisms.
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Biologists have discovered universal mechanisms of cellular regulation involving the
same small set of cell-signaling mechanisms.
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The ubiquity of these mechanisms provides additional evidence for the evolutionary
relatedness of all life.
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Cells most often communicate by chemical signals, although signals may take other
forms.
Concept 11.1 External signals are converted into responses within the cell
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What messages are passed from cell to cell? How do cells respond to these messages?
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We will first consider communication in microbes, to gain insight into the evolution of
cell signaling.
Cell signaling evolved early in the history of life.
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One topic of cell “conversation” is sex.
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Saccharomyces cerevisiae, the yeast of bread, wine, and beer, identifies potential mates
by chemical signaling.
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There are two sexes, a and ?, each of which secretes a specific signaling molecule, a
factor and ? factor, respectively.
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These factors each bind to receptor proteins on the other mating type.
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Once the mating factors have bound to the receptors, the two cells grow toward each
other and undergo other cellular changes.
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The two cells fuse, or mate, to form an a/? cell containing the genes of both cells.
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The process by which a signal on a cell’s surface is converted into a specific cellular
response is a series of steps called a signal-transduction pathway.
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The molecular details of these pathways are strikingly similar in yeast and animal
cells, even though their last common ancestor lived more than a billion years ago.
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Signaling systems of bacteria and plants also share similarities.
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These similarities suggest that ancestral signaling molecules evolved long ago in
prokaryotes and have since been adopted for new uses by single-celled eukaryotes and
multicellular descendents.
Communicating cells may be close together or far apart.

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Multicellular organisms release signaling molecules that target other cells.
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Cells may communicate by direct contact.
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Both animals and plants have cell junctions that connect to the cytoplasm of adjacent
cells.
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Signaling substances dissolved in the cytosol can pass freely between adjacent cells.
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Animal cells can communicate by direct contact between membrane-bound cell
surface molecules.
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Such cell-cell recognition is important to such processes as embryonic development
and the immune response.
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In other cases, messenger molecules are secreted by the signaling cell.