Final answer:
A hormone is a signaling molecule synthesized in one location that travels through the organism to elicit a response elsewhere, binding to specific receptors on target cells.
Step-by-step explanation:
A molecule that is synthesized in one part of an organism and then elicits a response at a different site is known as a hormone. Hormones are released in response to a stimulus and then travel through the body. They bind to either extracellular or intracellular receptors of target cells depending on their solubility. For example, a lipid-derived hormone is fat soluble and capable of passing through cell membranes to reach intracellular receptors. In contrast, peptide hormones, which are not fat soluble, typically bind to extracellular receptors.
Summing up, hormones like those released from the pituitary gland or the adrenal medulla play crucial roles in regulating various physiological processes by binding to specific receptors and initiating a cascade of cellular events.