1. Cell to Cell Communication via G-Protein Linked Receptors
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Cell to Cell Communication via G-Protein Linked Receptors
Packet #19
Chapter #11

2. Introduction
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G-protein-linked receptors and enzyme-linked receptors are used by practically every cell type of the body
G-protein linked receptors form the largest family of cell-surface receptors
G-protein-linked receptors are not found in bacteria
Signals received by G-protein-linked, or enzyme- linked receptors are transmitted to elaborate relay systems formed from cascades (a series) of intracellular signaling molecules

3. Introduction II G-protein-linked receptors
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G-protein-linked receptors
Mediate responses to an enormous diversity of extracellular signal molecules
Hormones
Local mediators
Neurotransmitters

4. G-Protein-Linked Receptors
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Bound ligand initiates a series of reactions that ultimately result in a specific intracellular response
Ligand
Molecule, such as a hormone or a neurotransmitter, that binds to a specific site on a protein.
Intracellular messenger systems, using cell receptors, function as signal amplification
Active receptor can activate many effector molecules

5. G Protein Linked Receptors
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6. Second Messenger Molecules
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G Proteins activate second messengers
Are small, nonprotein, water-soluble molecules or ions
Intervene between original message and the ultimate effect of the cell
Part of the cascade of events that translate binding hormone, or neurotransmitter, into a cellular response
Two mostly recognized second messenger systems
Adenylate cyclase system
Calcium/phosphatidylinositol system

7. cAMP Second Messenger
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8. Cyclic Adenosine Monophosphate
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9. Calcium ions and Inositol Triphosphate (IP3)
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Calcium, when released into the cytosol of a cell
Acts as a second messenger in many different pathways
Calcium is an important second messenger
Because cells are able to regulate its concentration in the cytosol

10. Calcium ions and Inositol Triphosphate (IP3) II
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11. Calcium ions and Inositol Triphosphate (IP3) III
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