Signal Molecules - Avon Community School Corporation
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Transcript Signal Molecules - Avon Community School Corporation
Chapter 11:
Cell
Communication
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).
Essential Knowledge
How do cells communicate?
◦ By “cellular” phones
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
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
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:
◦ Direct contact
◦ Through signal molecules
Reception
When molecules can flow directly from cell
to cell without crossing membranes
Plants - plasmodesmata
Animals - gap junctions
Direct Contact
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
Signal Molecules
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
Receptor Molecules
1. G-Protein linked
2. Tyrosine-Kinase
3. Ion channels
4. Intracellular
**You must research these on your own.
Receptor Molecules
Most signals never enter a cell
◦ The signal is received at the membrane and
passed on
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
Signal-Transduction Pathways
The addition of Pi to a protein, which
activates the protein
Usually adds Pi to Serine or Threonine
amino acids
Protein Phosphorylation
General name for any enzyme that
transfers Pi from ATP to a protein
About 1% of our genes are for Protein
Kinases
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.
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
Secondary Messengers
Response
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
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
Transcription
Regulation/Response
Chapter focused only on activating signals
There are also inactivation mechanisms to
stop signals
◦ We will learned about these with the cell cycle
Comment
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