Cell CommunicationChapter 11
Cellular MessagingCell-to-cell communication is
essential for both multicellular and unicellular organisms.
Cells can signal to each other and interpret the signals they receive from other cells and the environment.Signals include light, touch, and
chemicals.Biologists have discovered some
universal mechanisms of cellular regulation.The same small set of cell-
signaling mechanisms shows up again and again in diverse species.
The fight-or-flight response is triggered by a signaling molecule called epinephrine
11.1 External signals are converted to responses within the cell
Evolution of Cell Signaling: S. cerevisiaeThe yeast, Saccharomyces cerevisiae, has two mating
types, a and .Cells of different mating types locate each other via
secreted factors specific to each type.Each type secretes a specific factor that binds to
receptors only on the other type of cell.When exposed to each other’s mating factors, a pair of
opposite cell types fuse (mate).Offspring contains a combination of genetic material that
is advantageous.
Figure 11.2
Exchange of mating factors
Receptor factor
a factorYeast cell,mating type a
Yeast cell,mating type
Mating
New a/ cell
1
2
3
a
a
a/
Once received by the yeast cell surface receptor, a mating signal is changed, or transduced, into a form that brings about the cellular response of mating.
A signal transduction pathway is a series of steps by which a signal on a cell’s surface is converted into a specific cellular response.
Each cell type secretes a mating factor that binds to receptors on the other cell type.Binding of the factors to receptors induces changes in cells that leads to their fusion.
Evolution of Cell Signaling: BacteriaBacterial cells secrete molecules that can be detected
by other bacterial cells.Sensing the concentration of such signaling molecules
allows bacteria to monitor the local density of cells, called quorum sensing.
Quorum sensing allows bacterial populations to coordinate their behaviors in activities that require a given number of cells acting simultaneously.Example: biofilm formation.
Local and Long-Distance SignalingCells in a multicellular
organism communicate by chemical messengers.
Animal and plant cells have cell junctions that directly connect the cytoplasm of adjacent cells.
In local signaling, animal cells may communicate by direct contact, or cell-cell recognition.
In many other cases, animal cells communicate using local regulators, messenger molecules that travel only short distances.
In long-distance signaling, plants and animals use chemicals called hormones.
The ability of a cell to respond to a signal depends on whether or not it has a receptor specific to that signal.
Long-distance signaling
Endocrine cell Bloodvessel
Hormone travelsin bloodstream.
Target cellspecificallybinds hormone.
(c) Endocrine (hormonal) signaling
The Three Stages of Cell Signaling: A PreviewEarl W. Sutherland discovered how the
hormone epinephrine acts on cells.Sutherland suggested that cells receiving
signals went through three processes:ReceptionTransductionResponse
Plasma membrane
EXTRACELLULARFLUID
CYTOPLASM
Reception Transduction Response
Receptor
Signalingmolecule
Activationof cellularresponse
Relay molecules in a signal transductionpathway
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Concept Check1. Explain how signaling is involved in
ensuring that yeast cells fuse only with cells of the opposite mating type.
2. In liver cells, glycogen phosphorylase acts in which of the three stages of the signaling pathway associated with an epinephrine-initiated signal?