Once a receptor protein receives a signal, it undergoes a conformational change, which in turn launches a series of biochemical reactions within the cell. These intracellular signaling pathways, also called signal transduction cascades, typically amplify the message, producing multiple intracellular signals for every one receptor that is bound.
Activation of receptors can trigger the synthesis of small molecules called second messengers, which initiate and coordinate intracellular signaling pathways. One example is cAMP, a common second messenger which is involved in signal transduction cascades. cAMP is synthesized from ATP by the enzyme adenylyl cylase, which is in the cell membrane. The activation of adenylyl cyclase can result in the manufacture of hundreds or even thousands of cAMP molecules. These cAMP molecules activate the enzyme protein kinase A, which then phosphorylates multiple protein substrates by attaching phosphate groups to them.
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Activation of receptors can trigger the synthesis of small molecules called second messengers, which initiate and coordinate intracellular signaling pathways. One example is cAMP, a common second messenger which is involved in signal transduction cascades. cAMP is synthesized from ATP by the enzyme adenylyl cylase, which is in the cell membrane. The activation of adenylyl cyclase can result in the manufacture of hundreds or even thousands of cAMP molecules. These cAMP molecules activate the enzyme protein kinase A, which then phosphorylates multiple protein substrates by attaching phosphate groups to them.
Animation-
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120069/bio08.swf::Signal%20Amplification