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Chapter 11
Cell Communication
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Overview: The Cellular Internet
• Cell-to-cell communication
– Is absolutely essential for multicellular
organisms
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• Biologists
– Have discovered some universal mechanisms
of cellular regulation
Figure 11.1
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• Concept 11.1: External signals are converted
into responses within the cell
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A. Cell Signaling
• Yeast cells
– Identify their mates by cell signaling
1 Exchange of
mating factors.
Each cell type
secretes a
mating factor
that binds to
receptors on
the other cell
type.
2 Mating. Binding
of the factors to
receptors
induces changes
in the cells that
lead to their
fusion.
 factor
Receptor

a
Yeast cell,  factor Yeast cell,
mating type a
mating type 

a
3 New a/ cell.
Figure 11.2
The nucleus of
the fused cell
includes all the
genes from the
a and a cells.
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a/
Local and Long-Distance Signaling
• Cells in a multicellular organism
– Communicate via chemical messengers
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B. Cell Junctions
• Animal and plant cells
– Have cell junctions that directly connect the
cytoplasm of adjacent cells
Plasma membranes
Gap junctions
between animal cells
Plasmodesmata
between plant cells
Figure 11.3 (a) Cell junctions. Both animals and plants have cell junctions that allow molecules
to pass readily between adjacent cells without crossing plasma membranes.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
C. Local Signaling
• In local signaling, animal cells
– May communicate via direct contact
Figure 11.3 (b) Cell-cell recognition. Two cells in an animal may communicate by interaction
between molecules protruding from their surfaces.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
C. Local Signaling (Paracrine and Synaptic)
• In other cases, animal cells
– Communicate using local regulators
Local signaling
Target cell
Electrical signal
along nerve cell
triggers release of
neurotransmitter
Neurotransmitter
diffuses across
synapse
Secretory
vesicle
Local regulator
diffuses through
extracellular fluid
Figure 11.4 A B
(a) Paracrine signaling. A secreting cell acts
on nearby target cells by discharging
molecules of a local regulator (a growth
factor, for example) into the extracellular
fluid.
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Target cell
is stimulated
(b) Synaptic signaling. A nerve cell
releases neurotransmitter molecules
into a synapse, stimulating the
target cell.
D. Long Distance Signaling
• In long-distance signaling
– Both plants and animals use hormones
Long-distance signaling
Endocrine cell
Blood
vessel
Hormone travels
in bloodstream
to target cells
Target
cell
Figure 11.4
(c) Hormonal signaling. Specialized
endocrine cells secrete hormones
into body fluids, often the blood.
Hormones may reach virtually all
C body cells.
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D.I. Steroid Hormone Action
• Steroid hormones
– Bind to intracellular receptors
Hormone
EXTRACELLULAR
(testosterone) FLUID
1 The steroid
hormone testosterone
passes through the
plasma membrane.
Plasma
membrane
Receptor
protein
Hormonereceptor
complex
2 Testosterone binds
to a receptor protein
in the cytoplasm,
activating it.
3 The hormone-
DNA
receptor complex
enters the nucleus
and binds to specific
genes.
mRNA
4 The bound protein
NUCLEUS
stimulates the
transcription of
the gene into mRNA.
New protein
5 The mRNA is
Figure 11.6
CYTOPLASM
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translated into a
specific protein.
D.II. Protein (Peptide) Hormone
• Overview of cell signaling
EXTRACELLULAR
FLUID
1 Reception
CYTOPLASM
Plasma membrane
2 Transduction
3 Response
Receptor
Activation
of cellular
response
Relay molecules in a signal transduction pathway
Signal
molecule
Figure 11.5
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
D.II. Protein (Peptide) Hormones
• Many G-proteins
– Trigger the formation of cAMP, which then acts
as a second messenger in cellular pathways
First messenger
(signal molecule
such as epinephrine)
G protein
G-protein-linked
receptor
Adenylyl
cyclase
GTP
ATP
cAMP
Protein
kinase A
Cellular responses
Figure 11.10
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D.II. Protein (Peptide) Hormones
• G-protein-linked receptors
Signal-binding site
The activated G-protein binds
another protein and alters its
function
Segment that
interacts with
G proteins
G-protein-linked
Receptor
Plasma Membrane
Activated
Receptor
Signal molecule
GDP
CYTOPLASM
G-protein
(inactive)
Enzyme
GDP
GTP
Activated
enzyme
GTP
GDP
Pi
Figure 11.7
Cellular response
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Inctivate
enzyme
Miscellaneous Receptors
• Receptor tyrosine kinases
Signal-binding sitea
Signal
molecule
Signal
molecule
Helix in the
Membrane
Tyr
Tyrosines
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Receptor tyrosine
kinase proteins
(inactive monomers)
CYTOPLASM
Tyr
Dimer
Activated
relay proteins
Figure 11.7
Tyr
P Tyr
P Tyr
Tyr P
Tyr P
Tyr
P Tyr
Tyr P
Tyr
Tyr
Tyr
Tyr
6
ATP
Activated tyrosinekinase regions
(unphosphorylated
dimer)
6 ADP
Fully activated receptor
tyrosine-kinase
(phosphorylated
dimer)
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P Tyr
P Tyr
P Tyr
Tyr P
Tyr P
Tyr P
Inactive
relay proteins
Cellular
response 1
Cellular
response 2
Miscellaneous Receptors
• Ion channel receptors
Signal
molecule
(ligand)
Gate
closed
Ions
Ligand-gated
ion channel receptor
Plasma
Membrane
Gate open
Cellular
response
Gate close
Figure 11.7
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• A phosphorylation cascade
Signal molecule
Receptor
Activated relay
molecule
Inactive
protein kinase
1
1 A relay molecule
activates protein kinase 1.
2 Active protein kinase 1
transfers a phosphate from ATP
to an inactive molecule of
protein kinase 2, thus activating
this second kinase.
Active
protein
kinase
1
Inactive
protein kinase
2
ATP
Pi
PP
Inactive
protein kinase
3
5 Enzymes called protein
phosphatases (PP)
catalyze the removal of
the phosphate groups
from the proteins,
making them inactive
and available for reuse.
Figure 11.8
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P
Active
protein
kinase
2
ADP
3 Active protein kinase 2
then catalyzes the phosphorylation (and activation) of
protein kinase 3.
ATP
ADP
Pi
Active
protein
kinase
3
PP
Inactive
protein
P
4 Finally, active protein
kinase 3 phosphorylates a
protein (pink) that brings
about the cell’s response to
the signal.
ATP
ADP
Pi
PP
P
Active
protein
Cellular
response
• Other pathways
– Regulate genes by activating transcription
factors that turn genes on or off
Growth factor
Reception
Receptor
Phosphorylation
cascade
Transduction
CYTOPLASM
Inactive
transcription Active
transcription
factor
factor
P
Response
DNA
Gene
Figure 11.14
NUCLEUS
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mRNA