In a receptor binding study, what does B represent?

In a receptor binding study, what does B represent?

• A. Drug bound to receptors
• B. Receptor density
• C. Unbound ligand
• D. Receptor activation state

Answer: (A)

In a receptor binding study, B is the amount of ligand that has bound to receptor sites. It represents receptor occupancy—the portion of drug that attaches to receptors at a given ligand concentration. This binding readout reflects receptor density (through Bmax) and affinity (through Kd). The unbound ligand is the free portion in solution, and receptor activation state refers to the functional response that may follow binding, not the binding amount itself. So the correct interpretation is the drug bound to receptors.

In a receptor binding study, B is the amount of ligand that has bound to receptor sites. It represents receptor occupancy—the portion of drug that attaches to receptors at a given ligand concentration. This binding readout reflects receptor density (through Bmax) and affinity (through Kd). The unbound ligand is the free portion in solution, and receptor activation state refers to the functional response that may follow binding, not the binding amount itself. So the correct interpretation is the drug bound to receptors.