Chapter 11:
Cell
Communication
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2.e.2 – Timing and coordination of physiological
events are regulated by multiple mechanisms
(11.1).
3.b.2 – A variety of intercellular and intracellular
signal transmissions mediate gene expression
(11.1 & 11.4).
3.d.1 – Cell communication processes share
common features that reflect a shared
evolutionary history (11.2 & 11.2).
3.d.2 – Cells communicate with each other
through direct contact with other cells or from a
distance via chemical signaling (11.1 & 11.2).
Essential Knowledge
3.d.3 – Signal transduction pathways link
signal reception with cellular response
(11.3).
 3.d.4 – Changes in signal transduction
pathways can alter cellular response
(11.4).
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Essential Knowledge
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How do cells communicate?
◦ By “cellular” phones 
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But seriously, cells do need to
communicate for many reasons.
Question?
Cell Communication
Regulation - cells need to control cellular
processes
 Environmental Stimuli - cells need to be
able to respond to signals from their
environment
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Why do cells communicate?
Is a relatively “new” topic in Biology and
AP Biology
 Appears to answer many questions in
medicine
 Is a topic you’ll be hearing more about in
your future
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Cell Signaling (C.S.)
1. Reception - receiving the signal
2. Transduction - passing on the signal
3. Response - cellular changes because of
the signal
Stages of cell signaling
Reception
The target cell’s detection of a signal
coming from outside the cell
 May occur by:
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◦ Direct contact
◦ Through signal molecules
Reception
When molecules can flow directly from cell
to cell without crossing membranes
 Plants - plasmodesmata
 Animals - gap junctions
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Direct Contact
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May also occur by cell surface molecules
that project from the surface and “touch”
another cell
Direct Contact
The actual chemical signal that travels
from cell to cell
 Often water soluble
 Usually too large to travel through
membranes
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Signal Molecules
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Behave as “ligands”
◦ A smaller molecule that binds to a larger one
Signal Molecules
Usually made of protein
 Change shape when bind to a signal
molecule
 Transmits information from the exterior to
the interior of a cell
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Receptor Molecules
1. G-Protein linked
2. Tyrosine-Kinase
3. Ion channels
4. Intracellular
**You must research these on your own.
Receptor Molecules
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Most signals never enter a cell
◦ The signal is received at the membrane and
passed on
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Exception - intracellular receptors
Comment
Transduction
The further amplification and movement
of a signal in the cytoplasm
 Often has multiple steps using relay
proteins such as Protein Kinases
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Signal-Transduction Pathways
The addition of Pi to a protein, which
activates the protein
 Usually adds Pi to Serine or Threonine
amino acids
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Protein Phosphorylation
General name for any enzyme that
transfers Pi from ATP to a protein
 About 1% of our genes are for Protein
Kinases
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Protein Kinase
Protein Kinases often work in a cascade
with each being able to activate several
molecules.
 Result - from one signal, many molecules
can be activated.
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Amplification
Small water soluble non-protein molecules
or ions that pass on a signal
 Spread rapidly by diffusion
 Activates relay proteins
 Ex: cAMP, Ca +2
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Secondary Messengers
Response
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May involve:
◦ Regulation of cytoplasmic activities
OR
◦ Regulation of transcription
Responses
Rearrangement of the cytoskeleton
 Opening or closing of an ion channel
 Alteration of cell metabolism
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Cytoplasmic Regulation/Response
Otherwise known as nuclear
regulation/reponse
 Activating protein synthesis for new
enzymes
 Transcription control factors are often
activated by a Protein Kinase
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Transcription
Regulation/Response
Chapter focused only on activating signals
 There are also inactivation mechanisms to
stop signals
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◦ We will learned about these with the cell cycle
Comment
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Recognize several examples and
importances of cell communication.
Identify the three stages of cell signaling.
Recognize how signals are received.
Recognize how signals are transduced.
Recognize the role of protein kinases and
phosphorylation in signal amplification
Identify how cells respond to signals.
Recognize the role of cell signaling in
apoptosis.
Summary