Chapter 11
Cell Communication
Single Transduction Pathway
• The process in which a signal on a cells surface
is converted into a specific cellular response
through a series of steps
Communicating Short Distances
• Local regulator: transmitting cell secretes
these that influence cells in the vicinity
– Growth factors
• Stimulate nearby target cells to grow and multiply
– Panacrine signaling
– Neurotransmitters
• Specific nerve cells are so close together, a signal can
travel great distances without affecting the wrong parts
• Direct contact
Communicating Long Distances
• Hormones (endocrine signaling)
– Specialized cells release hormone molecules into
vessels of the circulatory system how they travel
to their target cells
Three Stages of Cell Signaling
1. Reception
– Target cell’s detection of a signal from outside the
cell
– It is detected when it binds to a cellular protein at
the cell’s surface
2. Transduction
– Binding of signal molecule initiates the process
– Converts signal to a form that can bring about a
response
3. Response
– Transduced signal triggers a specific cellular response
Reception
• Signal molecule behaves as a ligand
– Binding generally causes a receptor protein to
undergo a change in shape
– Shape change directly activates the receptor so
that it can interact with another cellular molecule
• Most receptors are membrane proteins
– G-Protein-linked receptor
– Tyrosine-kinase receptors
– Ion-channel receptors
G-Protein-Linked Receptors
• Plasma membrane receptor that works with help
of G protein
• Vary in their binding sites for recognizing signal
molecules and for recognizing different G
proteins inside the cell
• G protein functions as a switch
1.
2.
3.
4.
Receptor is activated
Causes a protein change
Binds to another protein and alters its activity
Triggers the next step in the pathway
Tyrosine-Kinase Receptors
• Part of it functions as an enzyme
1. Ligand binds causing two receptor
polypeptides to aggregate, forming a dimer