Final answer:
Hydrophilic hormones, including amino acid-derived and polypeptide hormones, bind to membrane surface receptors to trigger a signal transduction cascade using a second messenger system like cAMP, leading to cellular responses, as these hormones cannot cross the lipid cell membrane.
Step-by-step explanation:
Hormones that cannot cross lipid-based cell membranes due to their water-soluble nature, such as amino acid-derived hormones and polypeptide hormones (excluding thyroid hormones), must bind to membrane surface receptors.
These receptors, often associated with a G protein, are essential for transmitting the hormone's signal into the cell. Upon hormone binding, the receptor activates a signal transduction process which often involves a second messenger system.
In the context of the epinephrine signaling pathway, for example, epinephrine binds to its receptor on the cell surface, initiating a cascade of intracellular events. Upon activation by the hormone, the G protein in turn activates cyclic adenosine monophosphate (cAMP), serving as a second messenger.
This second messenger system greatly amplifies the initial hormone signal and accelerates the cellular response, which could include processes like the conversion of glycogen to glucose.
Lipid insoluble hormone receptors are thus vital for initiating this biological response without the hormone itself entering the cell. This is in contrast to lipid-soluble hormones, such as steroid hormones, which can directly cross the cell membrane and interact with DNA within the nucleus to regulate gene transcription.