What term describes molecules that bind to the receptor of the cell and block the action of an agonist?

The term that describes molecules that bind to the receptor of a cell and prevent the action of an agonist is "antagonist." Antagonists have a specific affinity for a receptor but do not activate it; instead, they block the receptor, inhibiting the intended biological response that would normally be triggered by an agonist. This blocking action can help regulate physiological processes by preventing overactivation of receptors or by competing with agonists for receptor binding sites.

In contrast, agonists are molecules that bind to receptors and activate them, leading to a biological response. Stimulants typically increase activity within the nervous system or enhance certain physiological functions, while modulators can refer to substances that modify the signal between agonists and receptors without directly blocking or activating the receptors. Each of these terms relates to how substances interact with receptors, but an antagonist specifically serves the role of blocking receptor activity initiated by agonists.