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Cell Communication II
Chapter 15
An animal cell depends on extracellular signals
to survive or divide
An animal cell depends on extracellular signals to
differentiate. Without extracellular signals the cell
will die
Signaling molecules must be turned over rapidly;
if turnover time is one minute concentration can decrease rapidly
Extracellular signaling molecules can bind to
intracellular receptors
Acetyl choline causes release of NO which
results in rapid relaxation of smooth muscle cells
Signaling molecules that bind to nuclear
receptors are small and hydrophobic
Inhibitory proteins make receptor inactive when
not bound to the signaling molecule
When signaling molecule binds receptor binds
DNA and increases gene transcription
Nuclear receptors have a DNA binding domain
Extracellular signaling molecules can bind to cell
surface receptors
3 large classes of cell surface receptors; ion
channel linked receptors
Active Chemical Synapse
3 large classes of cell surface receptors; G
protein linked receptors
3 large classes of cell surface receptors; enzyme
linked receptors
G-protein linked receptor
The structure of an inactive G-protein
Without signaling molecule G-protein is inactive
G-protein binds to receptor when signaling
molecule is present
G-protein accepts GTP and disassemble into two
active subunits
The α subunit of the G-protein can be
deactivated through hydrolysis of GTP
Deactivation of G-protein
Reassembly of α subunit with other 2 subunits
reforms inactive G-protein complex
Arrestin binds phosphorylated G-protein receptor
and deactivates the receptor and prepares it for
endocytosis
DVD clip 61
Release of cAMP inside cell caused by
serentonin and mediated by a G-protein
Synthesis and degradation of cyclic AMP
Activation of cAMP dependent protein kinase
Activation of gene transcription by cAMP
Activation of gene transcription by cAMP