Which forces determine the binding of a drug to a receptor?

• A. Hydrogen bonds only
• B. Hydrogen bonds, ionic bonds, van der waals forces, and covalent bonds
• C. Ionic bonds only
• D. Covalent bonds only

Answer: (B)

Drug–receptor binding is governed by a mix of interactions, not a single type. Hydrogen bonds provide directionality and specificity by linking donor and acceptor groups in the binding site. Ionic interactions contribute strong electrostatic attraction between oppositely charged groups. Van der Waals forces come from close-contact attractions that add up over the contact surface, shaping fit and stability. Covalent bonds can occur in some cases, creating a permanent attachment between the drug and receptor. Because real binding often relies on multiple simultaneous interactions, all of these forces can contribute to the binding event, making the combination of hydrogen bonds, ionic interactions, van der Waals forces, and covalent bonds the best description of how a drug binds to a receptor.