The interaction of a drug with a receptor initiates a chain of events leading to what?

• A. Immediate cell death
• B. No cellular response
• C. The drug's observed effects
• D. Random chemical reactions

Answer: (C)

When a drug binds to its receptor, that binding acts as the trigger for signaling inside the cell. The receptor changes shape and activates intracellular pathways—such as second messengers, ion channel changes, or kinase cascades—that alter cellular function. This activated signaling chain ultimately produces the drug’s observable effects on tissue and organism, rather than causing immediate cell death or no response. The specifics of the response depend on which receptor is engaged and where it is in the body, but the common idea is that receptor activation converts a chemical signal into a controlled cellular response.