What term describes a drug that activates a receptor or enzyme?

The term that describes a drug that activates a receptor or enzyme is "agonist." Agonists bind to specific receptors or enzymes in the body and initiate a biological response, effectively mimicking the action of a naturally occurring substance. This response can lead to various physiological effects, depending on the receptor or enzyme affected and the tissue involved.

In the context of pharmacology, agonists are important because they can enhance or replicate physiological processes. For example, in the case of neurotransmitter receptors, agonists can increase the effects of neurotransmitters, potentially leading to enhanced signaling pathways and biological responses.

While other options might have related meanings, they represent different actions: antagonists block or inhibit receptor activity, partial agonists activate receptors but to a lesser degree than full agonists, and inhibitors reduce the activity of enzymes without directly activating them. Understanding these distinctions is key to grasping how various drugs can influence bodily functions and therapeutic outcomes.