AP BIOLOGY

Detailed explanation-1: -The signal transduction cascade begins when adenylyl cyclase, a membrane-bound enzyme, is activated by G-protein molecules associated with the adrenergic receptor. Adenylyl cyclase creates multiple cyclic AMP molecules, which fan out and activate protein kinases (PKA, in this example).

Detailed explanation-2: -Gene pathways, networks, and their regulation Signal transduction pathway involves the binding of extracellular signaling molecules and ligands to receptors located on the cell surface or inside the cell that trigger events inside the cell, to invoke a response.

Detailed explanation-3: -Most enzymes involved in cell signaling, such as protein kinases, protein phosphatases, GTPases, and nucleotide cyclases catalyze nucleophilic substitutions at phosphorus. When possible, the mechanisms of such enzymes are most clearly described quantitatively in terms of how associative or dissociative they are.