What is the role of receptor in drug action?

• A. A regulatory protein that accelerates chemical reactions in the body
• B. A regulatory molecule to which a drug binds to elicit a response
• C. A transporter that moves drugs across membranes
• D. An enzyme that metabolizes drugs

Answer: (B)

Receptors are the body's signaling proteins. They are typically a protein on the cell surface or inside the cell that recognizes and binds a drug (or endogenous molecule). When the drug binds, the receptor undergoes a change that triggers a cellular response—activating or inhibiting signaling pathways and producing the drug’s effect. This is why drugs work by targeting these receptors, with some acting as agonists (turning the receptor on) and others as antagonists (blocking the receptor).

The other roles described belong to different proteins: enzymes that speed up chemical reactions, transporters that move substances across membranes, or enzymes that metabolize drugs. Those functions aren’t the receptor-mediated signal that underlies most drug actions.