Which statement about receptor binding is true?

Which statement about receptor binding is true?

• A. Binding is determined solely by dose.
• B. Binding is determined by the molecular features of the drug.
• C. Binding is determined by the color of the pill.
• D. Binding is determined by the time of administration.

Answer: (B)

Binding is determined by the molecular features of the drug. The receptor’s binding site has a specific shape and chemical environment, so the drug must fit well and present the right functional groups to form noncovalent interactions (such as hydrogen bonds, ionic contacts, and hydrophobic interactions). This compatibility sets the drug’s affinity for the receptor—the tighter the fit and the stronger the interactions, the higher the affinity. Dose matters for how much drug is available to bind, and thus how many receptors become occupied, but it does not change the inherent fit between the drug and the receptor. Pill color and the time of administration don’t influence the molecular interactions at the receptor binding site. In other words, binding is about molecular compatibility and affinity, while dose controls occupancy given that compatibility.

Binding is determined by the molecular features of the drug. The receptor’s binding site has a specific shape and chemical environment, so the drug must fit well and present the right functional groups to form noncovalent interactions (such as hydrogen bonds, ionic contacts, and hydrophobic interactions). This compatibility sets the drug’s affinity for the receptor—the tighter the fit and the stronger the interactions, the higher the affinity.

Dose matters for how much drug is available to bind, and thus how many receptors become occupied, but it does not change the inherent fit between the drug and the receptor. Pill color and the time of administration don’t influence the molecular interactions at the receptor binding site. In other words, binding is about molecular compatibility and affinity, while dose controls occupancy given that compatibility.