Signal Transduction: Getting The Message Across

8.11.05

Signal transduction
Plasma membrane = information barrier.

First messenger (outside) ⇒ Binds to receptor ⇒ Second messenger (inside) ⇒ Change in biochemical activity.

Excitation-contraction coupling - excitable cells (eg. nerves, muscles); action potential.
Stimulus-secretion coupling - non-excitable cells (eg. saliva).

The nature of the biological response depends on the cell type.
-NOT the second messenger.
-NOT the cell surface receptor.

Sympathetic response - noradrenaline ⇒ cAMP ⇒ protein.
Parasympathetic response - acetylcholine ⇒ Ca2+ ⇒ fluid.

Summary
• Signal transduction = process that enables cells to respond to changes in their environment.
• Second messenger pathways
-flexibility
-amplification
filtering.