cell communication

Cell Communication
Chapter 11
• Cells need to communicate between
themselves to maintain
• Process by which signal on cell’s
surface converted into specific
cellular response consists of series
of steps - signal-transduction
• 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
• 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
• 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.
• 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
• Some signals diffuse through
plasma membrane; don’t need
• 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.
• Response of particular cell to signal
depends on particular collection of
• Some pathways actually linked by
scaffolding proteins - allows signals
to be passed through pathways.
• All proteins involved in signal
pathway important - defects in any
can cause abnormal signals.