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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
Cell-to-Cell Communication
Cell-to-cell communication is absolutely
essential for multicellular organisms
• Biologists have discovered some universal
mechanisms of cellular regulation
Viagra
(multicolored) is
bound to an
enzyme (purple)
in a signaling
pathway
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• External signals are
converted into responses
within the cell
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• Signal Transduction Pathways
– Convert signals on a cell’s
surface into cellular
responses
– Are similar in microbes and
mammals, suggesting an early
origin
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Local and Long-Distance Signaling
• Cells in a multicellular organism
– Communicate via chemical
messengers
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Communication by Direct Contact
Between Cells
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• 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.
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Local and long-distance cell
communication in animals
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• The hormone epinephrine
– Has multiple effects in mediating the
body’s response to short-term stress
Different receptors
different cell responses
Epinephrine
Epinephrine
Epinephrine
a receptor
b receptor
b receptor
Glycogen
deposits
Vessel
dilates
Vessel
constricts
(a) Intestinal blood
vessel
Glycogen
breaks down
and glucose
is released
from cell
(b) Skeletal muscle
blood vessel
Different
intracellular
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as Benjamin
Cummings
proteins
(c) Liver cell
different cell responses
Overview of Cell Signaling
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• Reception: A signal molecule
binds to a receptor protein,
causing it to change shape
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• The binding between signal
molecule (ligand) and receptor is
highly specific
• A conformational change in a
receptor is often the initial
transduction of the signal
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Chemical Signaling Mechanisms and Amplification
• https://neuroscience5e.sinauer.com/animations
07.01.html
• http://www.biologyalive.com/life/classes/apbiolo
gy/documents/Unit%204/11_Lectures_PPT/me
dia/11_05SignalingOverview_A.swf
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Intracellular receptors are
cytoplasmic or nuclear proteins
• Signal molecules that are small
or hydrophobic can readily
cross the plasma membrane use
these receptors
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Steroid hormone interacting with
an intracellular receptor
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Action of Steroid Hormones:
• http://highered.mheducation.com/sites/007299
5246/student_view0/chapter12/mechanism_of_
steroid_hormone_action.html
• http://highered.mheducation.com/sites/007299
5246/student_view0/chapter12/how_intracellul
ar_receptors_regulate_gene_transcription.html
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Receptors in the Plasma Membrane
• There are three main types of membrane
receptors:
• G-Protein-Linked: (epinephrine,
neurotransmitters, pertussis, botulism,
cholera)
• Tyrosine Kinases: (cell growth and
reproduction)
• Ion Channels: (neurotransmitters, Na+,
Ca++
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The Structure of a G-Protein-Linked Receptor
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The Functioning of a G-protein-Linked
Receptor
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Membrane-Bound Receptors That Activate G Proteins:
http://novella.mhhe.com/sites/0070070017/student_view0/biology_1/chapt
er_11/membrane-bound_receptors_that_activate_g_proteins.html
http://highered.mheducation.com/sites/9834092339/student_
view0/chapter46/membranebound_receptors_that_activate_g_proteins.html
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The Structure and Function of a
Tyrosine-Kinase Receptor
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A Ligand-Gated Ion-Channel Receptor
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• Transduction: Cascades of
molecular interactions relay signals
from receptors to target molecules
in the cell
• Multistep pathways can amplify a
signal and provide more
opportunities for coordination and
regulation
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Signal Transduction Pathways
• At each step in a pathway the
signal is transduced into a
different form, commonly a
conformational change in a
protein
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Protein Phosphorylation and Dephosphorylation
• Many signal pathways include
phosphorylation cascades
• In this process a series of protein
kinases add a phosphate to the
next one in line, activating it
– Phosphatase enzymes then
remove the phosphates
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A Phosphorylation Cascade
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Small Molecules and Ions as Second Messengers
• Second messengers are small,
nonprotein, water-soluble
molecules or ions
• Cyclic AMP (cAMP) -made from ATP
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cAMP as a Second Messenger
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Secondary Messengers: cAMP
• http://novella.mhhe.com/sites/0070070017/stud
ent_view0/biology_1/chapter_11/second_mess
enger__camp.html
• G Proteins and Signal Amplification:
http://novella.mhhe.com/sites/0070070017/stude
nt_view0/biology_1/chapter_45/signal_amplificati
on.html
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Calcium ions and Inositol Triphosphate (IP3)
• Calcium, when released into the
cytosol of a cell, acts as a
second messenger in many
different pathways
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The maintenance of calcium ion
concentrations in an animal cell
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• Other second messengers such
as inositol triphosphate (IP3)
and diacylglycerol (DAG) can
trigger an increase in calcium
in the cytosol
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Calcium and Inositol Triphosphate in
Signaling Pathways
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• Response: Cell signaling leads
to regulation of cytoplasmic
activities or transcription
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Cytoplasmic response to a signal: the
stimulation of glycogen breakdown by
epinephrine
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Nuclear response to a signal: the activation of
a specific gene by a growth factor
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Fine-Tuning of the Response
• Signal pathways with multiple
steps can amplify the signal and
contribute to the specificity of
the response
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Signal Amplification
• Each protein in a signaling
pathway amplifies the signal by
activating multiple copies of the
next component in the pathway
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Signal Amplification:
• http://novella.mhhe.com/sites/0070070017/stud
ent_view0/biology_1/chapter_45/signal_amplifi
cation.html
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The Specificity of Cell Signaling
• The different combinations of
proteins in a cell give the cell
great specificity in both the
signals it detects and the
responses it carries out
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The Specificity of Cell Signaling
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Scaffolding Proteins Increase
Transduction Efficiency
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Termination of the Signal
• Signal response is terminated
quickly by the reversal of ligand
binding
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings