Ch 11: Cell Communication

AP Biology Powerpoint Presentations: 9th Edition

1. LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
© 2011 Pearson Education, Inc.
Lectures by
Erin Barley
Kathleen Fitzpatrick
Cell Communication
Chapter 11

2. Overview: Cellular Messaging
•Cell-to-cell communication is essential for both
multicellular and unicellular organisms
•Biologists have discovered some universal
mechanisms of cellular regulation
•Cells most often communicate with each other
via chemical signals
•For example, the fight-or-flight response is
triggered by a signaling molecule called
epinephrine
© 2011 Pearson Education, Inc.

3. Figure 11.1

4. Concept 11.1: External signals are
converted to responses within the cell
•Microbes provide a glimpse of the role of cell
signaling in the evolution of life
© 2011 Pearson Education, Inc.

5. Evolution of Cell Signaling
•The yeast, Saccharomyces cerevisiae, has two
mating types, a and a
•Cells of different mating types locate each other
via secreted factors specific to each type
•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
•Signal transduction pathways convert signals on
a cell’s surface into cellular responses
© 2011 Pearson Education, Inc.

6. Figure 11.2
Exchange
of mating
factors
Receptor
a factor
a factor
Yeast cell,
mating type a
Yeast cell,
mating type a
Mating
New a/a cell
1
2
3
a
a
a/a
a
a

7. •Pathway similarities suggest that ancestral
signaling molecules evolved in prokaryotes and
were modified later in eukaryotes
•The concentration of signaling molecules allows
bacteria to sense local population density
© 2011 Pearson Education, Inc.

8. Individual
rod-shaped
cells
Spore-forming
structure
(fruiting body)
Aggregation
in progress
Fruiting bodies
1
2
3
0.5 mm
2.5 mm
Figure 11.3

9. Figure 11.3a
Individual rod-shaped cells1

10. Figure 11.3b
Aggregation in progress2

11. Figure 11.3c
Spore-forming structure
(fruiting body)
0.5 mm
3

12. Figure 11.3d
Fruiting bodies
2.5 mm

13. Local and Long-Distance Signaling
•Cells 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
© 2011 Pearson Education, Inc.

14. Figure 11.4
Plasma membranes
Gap junctions
between animal cells
Plasmodesmata
between plant cells
(a) Cell junctions
(b) Cell-cell recognition

15. •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
© 2011 Pearson Education, Inc.

16. Figure 11.5
Local signaling Long-distance signaling
Target cell
Secreting
cell
Secretory
vesicle
Local regulator
diffuses through
extracellular fluid.
(a) Paracrine signaling (b) Synaptic signaling
Electrical signal
along nerve cell
triggers release of
neurotransmitter.
Neurotransmitter
diffuses across
synapse.
Target cell
is stimulated.
Endocrine cell
Blood
vessel
Hormone travels
in bloodstream.
Target cell
specifically
binds
hormone.
(c) Endocrine (hormonal) signaling

17. Figure 11.5a
Local signaling
Target cell
Secreting
cell
Secretory
vesicle
Local regulator
diffuses through
extracellular fluid.
(a) Paracrine signaling (b) Synaptic signaling
Electrical signal
along nerve cell
triggers release of
neurotransmitter.
Neurotransmitter
diffuses across
synapse.
Target cell
is stimulated.

18. Figure 11.5b
Long-distance signaling
Endocrine cell
Blood
vessel
Hormone travels
in bloodstream.
Target cell
specifically
binds
hormone.
(c) Endocrine (hormonal) signaling

19. The Three Stages of Cell Signaling:
A Preview
•Earl W. Sutherland discovered how the hormone
epinephrine acts on cells
•Sutherland suggested that cells receiving signals
went through three processes
–Reception
–Transduction
–Response
© 2011 Pearson Education, Inc.
Animation: Overview of Cell Signaling

20. Figure 11.6-1
Plasma membrane
EXTRACELLULAR
FLUID
CYTOPLASM
Reception
Receptor
Signaling
molecule
1

21. Figure 11.6-2
Plasma membrane
EXTRACELLULAR
FLUID
CYTOPLASM
Reception Transduction
Receptor
Signaling
molecule
Relay molecules in a signal transduction
pathway
21

22. Figure 11.6-3
Plasma membrane
EXTRACELLULAR
FLUID
CYTOPLASM
Reception Transduction Response
Receptor
Signaling
molecule
Activation
of cellular
response
Relay molecules in a signal transduction
pathway
321

23. Concept 11.2: Reception: A signaling
molecule binds to a receptor protein, causing
it to change shape
•The binding between a signal molecule (ligand)
and receptor is highly specific
•A shape change in a receptor is often the initial
transduction of the signal
•Most signal receptors are plasma membrane
proteins
© 2011 Pearson Education, Inc.

24. Receptors in the Plasma Membrane
•Most water-soluble signal molecules bind to
specific sites on receptor proteins that span the
plasma membrane
•There are three main types of membrane
receptors
–G protein-coupled receptors
–Receptor tyrosine kinases
–Ion channel receptors
© 2011 Pearson Education, Inc.

25. •G protein-coupled receptors (GPCRs) are the
largest family of cell-surface receptors
•A GPCR is a plasma membrane receptor that
works with the help of a G protein
•The G protein acts as an on/off switch: If GDP is
bound to the G protein, the G protein is inactive
© 2011 Pearson Education, Inc.

26. Figure 11.7a
G protein-coupled receptor
Signaling molecule binding site
Segment that
interacts with
G proteins

27. Figure 11.7b
G protein-coupled
receptor
21
3 4
Plasma
membrane
G protein
(inactive)
CYTOPLASM
Enzyme
Activated
receptor
Signaling
molecule
Inactive
enzyme
Activated
enzyme
Cellular response
GDP
GTP
GDP
GTP
GTP
P
i
GDP
GDP

28. Figure 11.8
Plasma
membrane
Cholesterol
b
2
-adrenergic
receptors
Molecule
resembling
ligand

29. •Receptor tyrosine kinases (RTKs) are
membrane receptors that attach phosphates to
tyrosines
•A receptor tyrosine kinase can trigger multiple
signal transduction pathways at once
•Abnormal functioning of RTKs is associated with
many types of cancers
© 2011 Pearson Education, Inc.

30. Figure 11.7c
Signaling
molecule (ligand)
21
3 4
Ligand-binding site
a helix in the
membrane
Tyrosines
CYTOPLASM Receptor tyrosine
kinase proteins
(inactive monomers)
Signaling
molecule
Dimer
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
Tyr
P
P
P
P
P
P
P
P
P
P
P
P
Activated tyrosine
kinase regions
(unphosphorylated
dimer)
Fully activated
receptor tyrosine
kinase
(phosphorylated
dimer)
Activated relay
proteins
Cellular
response 1
Cellular
response 2
Inactive
relay proteins
6 ATP6 ADP

31. •A ligand-gated ion channel receptor acts as a
gate when the receptor changes shape
•When a signal molecule binds as a ligand to the
receptor, the gate allows specific ions, such as
Na
+
or Ca
2+
, through a channel in the receptor
© 2011 Pearson Education, Inc.

32. Figure 11.7d
Signaling
molecule
(ligand)
21 3
Gate
closed
Ions
Ligand-gated
ion channel receptor
Plasma
membrane
Gate
open
Cellular
response
Gate closed

33. Intracellular Receptors
•Intracellular receptor proteins are found in the
cytosol or nucleus of target cells
•Small or hydrophobic chemical messengers can
readily cross the membrane and activate
receptors
•Examples of hydrophobic messengers are the
steroid and thyroid hormones of animals
•An activated hormone-receptor complex can act
as a transcription factor, turning on specific
genes
© 2011 Pearson Education, Inc.

34. Figure 11.9-1
Hormone
(testosterone)
Receptor
protein
Plasma
membrane
DNA
NUCLEUS
CYTOPLASM
EXTRACELLULAR
FLUID

35. Figure 11.9-2
Hormone
(testosterone)
Receptor
protein
Plasma
membrane
Hormone-
receptor
complex
DNA
NUCLEUS
CYTOPLASM
EXTRACELLULAR
FLUID

36. Figure 11.9-3
Hormone
(testosterone)
Receptor
protein
Plasma
membrane
Hormone-
receptor
complex
DNA
NUCLEUS
CYTOPLASM
EXTRACELLULAR
FLUID

37. Figure 11.9-4
Hormone
(testosterone)
Receptor
protein
Plasma
membrane
Hormone-
receptor
complex
DNA
mRNA
NUCLEUS
CYTOPLASM
EXTRACELLULAR
FLUID

38. Figure 11.9-5
Hormone
(testosterone)
Receptor
protein
Plasma
membrane
EXTRACELLULAR
FLUID
Hormone-
receptor
complex
DNA
mRNA
NUCLEUS
CYTOPLASM
New protein

39. Concept 11.3: Transduction: Cascades of
molecular interactions relay signals from
receptors to target molecules in the cell
•Signal transduction usually involves multiple steps
•Multistep pathways can amplify a signal: A few
molecules can produce a large cellular response
•Multistep pathways provide more opportunities for
coordination and regulation of the cellular
response
© 2011 Pearson Education, Inc.

40. Signal Transduction Pathways
•The molecules that relay a signal from receptor to
response are mostly proteins
•Like falling dominoes, the receptor activates
another protein, which activates another, and so
on, until the protein producing the response is
activated
•At each step, the signal is transduced into a
different form, usually a shape change in a protein
© 2011 Pearson Education, Inc.

41. Protein Phosphorylation and
Dephosphorylation
•In many pathways, the signal is transmitted by a
cascade of protein phosphorylations
•Protein kinases transfer phosphates from ATP to
protein, a process called phosphorylation
© 2011 Pearson Education, Inc.

42. •Protein phosphatases remove the phosphates
from proteins, a process called dephosphorylation
•This phosphorylation and dephosphorylation
system acts as a molecular switch, turning
activities on and off or up or down, as required
© 2011 Pearson Education, Inc.

43. Receptor
Signaling molecule
Activated relay
molecule
P
h
o
s
p
h
o
r
y
l
a
t
i
o
n

c
a
s
c
a
d
e
Inactive
protein kinase
1 Active
protein
kinase
1
Active
protein
kinase
2
Active
protein
kinase
3
Inactive
protein kinase
2
Inactive
protein kinase
3
Inactive
protein
Active
protein
Cellular
response
ATP
ADP
ATP
ADP
ATP
ADP
PP
PP
PP
P
P
P
P
i
P
i
P
i
Figure 11.10

44. Activated relay
molecule
P
h
o
s
p
h
o
r
y
l
a
t
i
o
n

c
a
s
c
a
d
e
Inactive
protein kinase
1 Active
protein
kinase
1
Active
protein
kinase
2
Active
protein
kinase
3
Inactive
protein kinase
2
Inactive
protein kinase
3
Inactive
protein
Active
protein
ATP
ADP
ATP
ADP
ATP
ADP
PP
PP
PP
P
P
P
i
P
i
P
i
P
Figure 11.10a

45. Small Molecules and Ions as Second
Messengers
•The extracellular signal molecule (ligand) that
binds to the receptor is a pathway’s “first
messenger”
•Second messengers are small, nonprotein, water-
soluble molecules or ions that spread throughout a
cell by diffusion
•Second messengers participate in pathways
initiated by GPCRs and RTKs
•Cyclic AMP and calcium ions are common second
messengers
© 2011 Pearson Education, Inc.

46. Cyclic AMP
•Cyclic AMP (cAMP) is one of the most widely
used second messengers
•Adenylyl cyclase, an enzyme in the plasma
membrane, converts ATP to cAMP in response to
an extracellular signal
© 2011 Pearson Education, Inc.

47. Figure 11.11
Adenylyl cyclase Phosphodiesterase
Pyrophosphate
AMP
H
2O
ATP
P
iP
cAMP

48. Figure 11.11a
Adenylyl cyclase
Pyrophosphate
ATP
P
iP
cAMP

49. Figure 11.11b
Phosphodiesterase
AMP
H
2
O
cAMP
H
2
O

50. •Many signal molecules trigger formation of cAMP
•Other components of cAMP pathways are G
proteins, G protein-coupled receptors, and protein
kinases
•cAMP usually activates protein kinase A, which
phosphorylates various other proteins
•Further regulation of cell metabolism is provided
by G-protein systems that inhibit adenylyl cyclase
© 2011 Pearson Education, Inc.

51. Figure 11.12
G protein
First messenger
(signaling molecule
such as epinephrine)
G protein-coupled
receptor
Adenylyl
cyclase
Second
messenger
Cellular responses
Protein
kinase A
GTP
ATP
cAMP

52. Calcium Ions and Inositol Triphosphate (IP
3
)
•Calcium ions (Ca
2+
) act as a second messenger in
many pathways
•Calcium is an important second messenger
because cells can regulate its concentration
© 2011 Pearson Education, Inc.

53. Figure 11.13
Mitochondrion
EXTRACELLULAR
FLUID
Plasma
membrane
Ca
2+
pump
Nucleus
CYTOSOL
Ca
2+
pump
Ca
2+
pump
Endoplasmic
reticulum
(ER)
ATP
ATP
Low [Ca
2+
]High [Ca
2+
]Key

54. •A signal relayed by a signal transduction pathway
may trigger an increase in calcium in the cytosol
•Pathways leading to the release of calcium involve
inositol triphosphate (IP
3
) and diacylglycerol
(DAG) as additional second messengers
© 2011 Pearson Education, Inc.
Animation: Signal Transduction Pathways

55. G protein
EXTRA-
CELLULAR
FLUID
Signaling molecule
(first messenger)
G protein-coupled
receptor
Phospholipase C
DAG
PIP
2
IP
3
(second messenger)
IP
3
-gated
calcium channel
Endoplasmic
reticulum (ER)
CYTOSOL
Ca
2+
GTP
Figure 11.14-1

56. Figure 11.14-2
G protein
EXTRA-
CELLULAR
FLUID
Signaling molecule
(first messenger)
G protein-coupled
receptor
Phospholipase C
DAG
PIP
2
IP
3
(second messenger)
IP
3
-gated
calcium channel
Endoplasmic
reticulum (ER)
CYTOSOL
Ca
2+
(second
messenger)
Ca
2+
GTP

57. Figure 11.14-3
G protein
EXTRA-
CELLULAR
FLUID
Signaling molecule
(first messenger)
G protein-coupled
receptor
Phospholipase C
DAG
PIP
2
IP
3
(second messenger)
IP
3
-gated
calcium channel
Endoplasmic
reticulum (ER)
CYTOSOL
Various
proteins
activated
Cellular
responses
Ca
2+
(second
messenger)
Ca
2+
GTP

58. Concept 11.4: Response: Cell signaling leads
to regulation of transcription or cytoplasmic
activities
•The cell’s response to an extracellular signal is
sometimes called the “output response”
© 2011 Pearson Education, Inc.

59. Nuclear and Cytoplasmic Responses
•Ultimately, a signal transduction pathway leads to
regulation of one or more cellular activities
•The response may occur in the cytoplasm or in the
nucleus
•Many signaling pathways regulate the synthesis of
enzymes or other proteins, usually by turning
genes on or off in the nucleus
•The final activated molecule in the signaling
pathway may function as a transcription factor
© 2011 Pearson Education, Inc.

60. Figure 11.15
Growth factor
Receptor
Reception
Transduction
CYTOPLASM
Response
Inactive
transcription
factor
Active
transcription
factor
DNA
NUCLEUS mRNA
Gene
Phosphorylation
cascade
P

61. •Other pathways regulate the activity of enzymes
rather than their synthesis
© 2011 Pearson Education, Inc.

62. Figure 11.16
Reception
Transduction
Response
Binding of epinephrine to G protein-coupled receptor (1 molecule)
Inactive G protein
Active G protein (10
2
molecules)
Inactive adenylyl cyclase
Active adenylyl cyclase (10
2
)
ATP
Cyclic AMP (10
4
)
Inactive protein kinase A
Active protein kinase A (10
4
)
Inactive phosphorylase kinase
Active phosphorylase kinase (10
5
)
Inactive glycogen phosphorylase
Active glycogen phosphorylase (10
6
)
Glycogen
Glucose 1-phosphate
(10
8
molecules)

63. •Signaling pathways can also affect the
overall behavior of a cell, for example,
changes in cell shape
© 2011 Pearson Education, Inc.

64. Wild type (with shmoos) DFus3 Dformin
Mating
factor
activates
receptor.
Mating
factor
G protein-coupled
receptor
Shmoo projection
forming
Formin
G protein binds GTP
and becomes activated.
2
1
3
4
5
P
P
P
P
ForminFormin
Fus3
Fus3Fus3
GDP
GTP
Phosphory-
lation
cascade
Microfilament
Actin
subunit
Phosphorylation cascade
activates Fus3, which moves
to plasma membrane.
Fus3 phos-
phorylates
formin,
activating it.
Formin initiates growth of
microfilaments that form
the shmoo projections.
RESULTS
CONCLUSION
Figure 11.17

65. Figure 11.17a
Wild type (with shmoos)

66. Figure 11.17b
DFus3

67. Figure 11.17c
Dformin

68. Fine-Tuning of the Response
•There are four aspects of fine-tuning to consider
–Amplification of the signal (and thus the response)
–Specificity of the response
–Overall efficiency of response, enhanced by
scaffolding proteins
–Termination of the signal
© 2011 Pearson Education, Inc.

69. Signal Amplification
•Enzyme cascades amplify the cell’s response
•At each step, the number of activated products is
much greater than in the preceding step
© 2011 Pearson Education, Inc.

70. The Specificity of Cell Signaling and
Coordination of the Response
•Different kinds of cells have different collections of
proteins
•These different proteins allow cells to detect and
respond to different signals
•Even the same signal can have different effects in
cells with different proteins and pathways
•Pathway branching and “cross-talk” further help
the cell coordinate incoming signals
© 2011 Pearson Education, Inc.

71. Figure 11.18
Signaling
molecule
Receptor
Relay
molecules
Response 1
Cell A. Pathway leads
to a single response.
Response 2Response 3 Response 4 Response 5
Activation
or inhibition
Cell B. Pathway branches,
leading to two responses.
Cell C. Cross-talk occurs
between two pathways.
Cell D. Different receptor
leads to a different
response.

72. Signaling
molecule
Receptor
Relay
molecules
Response 1
Cell A. Pathway leads
to a single response.
Response 2Response 3
Cell B. Pathway branches,
leading to two responses.
Figure 11.18a

73. Response 4 Response 5
Activation
or inhibition
Cell C. Cross-talk occurs
between two pathways.
Cell D. Different receptor
leads to a different
response.
Figure 11.18b

74. Signaling Efficiency: Scaffolding Proteins
and Signaling Complexes
•Scaffolding proteins are large relay proteins to
which other relay proteins are attached
•Scaffolding proteins can increase the signal
transduction efficiency by grouping together
different proteins involved in the same pathway
•In some cases, scaffolding proteins may also help
activate some of the relay proteins
© 2011 Pearson Education, Inc.

75. Figure 11.19
Signaling
molecule
Receptor
Plasma
membrane
Scaffolding
protein
Three
different
protein
kinases

76. Termination of the Signal
•Inactivation mechanisms are an essential aspect
of cell signaling
•If ligand concentration falls, fewer receptors will be
bound
•Unbound receptors revert to an inactive state
© 2011 Pearson Education, Inc.

77. Concept 11.5: Apoptosis integrates multiple
cell-signaling pathways
•Apoptosis is programmed or controlled cell
suicide
•Components of the cell are chopped up and
packaged into vesicles that are digested by
scavenger cells
•Apoptosis prevents enzymes from leaking out of a
dying cell and damaging neighboring cells
© 2011 Pearson Education, Inc.

78. Figure 11.20
2 mm

79. Apoptosis in the Soil Worm Caenorhabditis
elegans
•Apoptosis is important in shaping an organism
during embryonic development
•The role of apoptosis in embryonic development
was studied in Caenorhabditis elegans
•In C. elegans, apoptosis results when proteins that
“accelerate” apoptosis override those that “put the
brakes” on apoptosis
© 2011 Pearson Education, Inc.

80. Figure 11.21
Mitochondrion
Ced-9
protein (active)
inhibits Ced-4
activity
Receptor
for death-
signaling
molecule
Ced-4Ced-3
Inactive proteins
(a) No death signal
Death-
signaling
molecule
Ced-9
(inactive)
Cell
forms
blebs
Active
Ced-4
Active
Ced-3
Other
proteases
Nucleases
Activation
cascade
(b) Death signal

81. Figure 11.21a
Mitochondrion
Ced-9
protein (active)
inhibits Ced-4
activity
Receptor
for death-
signaling
molecule
Ced-4Ced-3
Inactive proteins
(a) No death signal

82. Death-
signaling
molecule
Ced-9
(inactive)
Cell
forms
blebs
Active
Ced-4
Active
Ced-3
Other
proteases
Nucleases
Activation
cascade
(b) Death signal
Figure 11.21b

83. Apoptotic Pathways and the Signals That
Trigger Them
•Caspases are the main proteases (enzymes that
cut up proteins) that carry out apoptosis
•Apoptosis can be triggered by
–An extracellular death-signaling ligand
–DNA damage in the nucleus
–Protein misfolding in the endoplasmic reticulum
© 2011 Pearson Education, Inc.

84. •Apoptosis evolved early in animal evolution and is
essential for the development and maintenance of
all animals
•Apoptosis may be involved in some diseases (for
example, Parkinson’s and Alzheimer’s);
interference with apoptosis may contribute to
some cancers
© 2011 Pearson Education, Inc.

85. Figure 11.22
Interdigital tissue
Cells undergoing
apoptosis
Space between
digits
1 mm

86. Figure 11.22a
Interdigital tissue

87. Figure 11.22b
Cells undergoing
apoptosis

88. Figure 11.22c
Space between
digits
1 mm

89. Figure 11.UN01
Reception1 2 3Transduction Response
Receptor
Signaling
molecule
Relay molecules
Activation
of cellular
response

90. Figure 11.UN02