Cell Communication
Chapter 11
• Cells need to communicate between
themselves to maintain
homeostasis.
• Process by which signal on cell’s
surface converted into specific
cellular response consists of series
of steps - signal-transduction
pathway.
http://www.mpi-dortmund.mpg.de/departments/dep1/signaltransduktion/image3.gif
• Yeasts communicate between 2
types of yeast cells to reproduce.
• 2 sexes, a and alpha - secrete
specific signaling molecule, a factor
and alpha factor.
• Factors find each other and bind to
each other’s receptors.
• Also occurs in multicellular
organisms.
• Some cells release local regulators
- influence cells in local vicinity.
• Synaptic signaling - nerve cell
produces neurotransmitter that
diffuses to single cell - is almost
touching sender.
• Nerve signals travel along series of
nerve cells without unwanted
responses from other cells.
• Plants, animals - hormones to signal
at greater distances.
• Cells may communicate by direct
contact.
• Signaling substances dissolved in
cytosol pass freely between
adjacent cells.
• 3 stages to signal transduction.
• 1Reception - chemical signal binds
to cellular protein at cell’s surface.
• 2Transduction - binding leads to
change in receptor that triggers
series of changes along signaltransduction pathway.
• 3Response - transduced signal
triggers specific cellular activity.
• Receptor proteins present on cells
to recognize signal molecules.
• Ligand - molecule that binds to
another molecule, causes cell to
change shape when attached to
cell’s receptor.
• Receptors usually found on plasma
membrane since signals can’t pass
through membrane.
http://www.slic2.wsu.edu:82/hurlbert/micro101/images/lock_key.gif
• 1 type - G-protein-linked-receptor.
• Acts as on/off switch; cycles
between being active and inactive.
• Tyrosine-kinase receptor system
helps different systems to function
at same time.
• System activated - activates other
systems at same time.
• Ligand-gated ion channels
open/close to allow chemical signals
to pass through.
• Important in nervous system - allow
Na+ and K+ move into and out of
cell.
http://dir.niehs.nih.gov/dirln/diricp/figures/overview.jpg
• Some signals diffuse through
plasma membrane; don’t need
proteins.
• Some are hormones which act on
transcription process.
• Transduction stage of signal
pathway allows for small signal to
be amplified - causes large signal.
• Protein kinases essential - help to
initiate responses.
• Some involve 2nd messengers molecules small enough to pass
through membrane.
http://www.du.edu/~kinnamon/3640/second_messengers/levitan11.2.jpg
• Response of particular cell to signal
depends on particular collection of
proteins.
• Some pathways actually linked by
scaffolding proteins - allows signals
to be passed through pathways.
http://www.bnl.gov/bnlweb/pubaf/pr/photos/2004/DNAbinding-300.jpg
• All proteins involved in signal
pathway important - defects in any
can cause abnormal signals.