1. Cellular Signaling
Ch. 11

2. Signal Transduction Pathway
First evolved in prokaryotes

3. Signal Types Local Signaling Long Distance – hormonal Paracrine
Synaptic
Long Distance – hormonal

4. Three Stages of Signaling
Reception
Ligands
Only specific cells respond
Transduction
Response

5. Common Components Protein kinase Phosphatase Phosphorylation Cascade
Amplify response
Scaffolding Protein

6. Types of Receptors Intracellular receptors
Receptors in the cellular membrane
G Protein linked receptors
Receptor tyrosine kinases
Ion channel receptors

7. Second Messengers
Small, non-protein water-soluble ions that send messages.
Amplify signal because many can be produced following primary messenger molecule
cAMP (cyclic adenosine monophosphate)
Formed from ATP when adenylyl cyclase is activated
Stimulates glycogen breakdown by activating protein kinase A
Broken down by phosphodiesterase

8. cAMP

9. Second Messengers
Ca++ and IP3 (inositol triphosphate) - Ca++ causes muscle cell contraction, cell division, and secretion of substances. Cytosolic concentrations maintained by pumps (to endoplasmic reticulum & mitochondria).
A G protein activates phospholipase C, which breaks PIP2 into DAG (diacylglycerol) and IP3.
IP3 opens the Ca++ gates, thereby activating proteins and causing cellular responses.

11. Types of Responses
Cytoplasmic responses
Nuclear responses