Final answer:
The signal molecule that elicits the strongest response from beta2 receptors is epinephrine, which is part of the fight-or-flight response mechanism.
Step-by-step explanation:
The signal molecule that elicits the stronger response from beta2 receptors is epinephrine. Epinephrine, also known as adrenaline, is an amino acid-derived hormone released from the adrenal medulla into the bloodstream, where it binds to beta-adrenergic receptors on the plasma membrane of cells. Upon binding, a G-protein is activated which in turn activates adenylyl cyclase, converting ATP to cAMP. cAMP acts as a second messenger initiating a cell-specific response, critical for the fight-or-flight response. Norepinephrine also binds to these receptors but typically elicits a less potent response than epinephrine.