AP BIOLOGY

Detailed explanation-1: -Adrenergic receptors are G protein-coupled receptors for epinephrine and norepinephrine. They are targets of many drugs for various conditions, including treatment of hypertension, hypotension, and asthma.

Detailed explanation-2: -For example, norepinephrine can act on either alpha-or beta-adrenergic receptors. Beta-adrenergic GPCRs couple to a stimulatory G-protein, or Gs, which initiates the cyclic AMP (cAMP) second messenger system by activating the enzyme adenylyl cyclase.

Detailed explanation-3: -Both epinephrine and norepinephrine activates both the alpha1 and alpha2 receptors. Alpha2 receptors also exist presynaptically associated with nerve terminals. Activation of these receptors inhibits the release of norepinephrine.

Detailed explanation-4: -Adrenergic receptors (also known as adrenoceptors, ARs) belong to the guanine nucleotide-binding G protein–coupled receptor (GPCR) superfamily, and are membrane receptors that activate heterotrimeric G proteins following the binding of a ligand.

Detailed explanation-5: -Norepinephrine can then go on to bind three main receptors: alpha1 (alpha-1), alpha-2, and beta receptors. These receptors classify as G-protein coupled receptors with either inhibitory or excitatory effects and different binding affinities to norepinephrine.