Lower Kd and higher Ka values correlate with what in receptor binding?

Lower Kd and higher Ka values correlate with what in receptor binding?

• A. Lower affinity.
• B. Higher affinity.
• C. Lower potency.
• D. Faster degradation.

Answer: (B)

Affinity is the strength of the interaction between a ligand and its receptor. A lower dissociation constant (Kd) means the ligand stays bound more readily, so you need less of the ligand to occupy half the receptors. A higher association constant (Ka) indicates the complex forms more readily, again pointing to tighter binding. Since Ka and Kd are effectively reciprocal (Ka ≈ 1/Kd), lowering Kd and raising Ka both reflect tighter binding. That tighter binding is what we mean by higher affinity. Potency and efficacy involve additional factors beyond just affinity, and degradation rate isn’t a direct measure of binding strength.

Affinity is the strength of the interaction between a ligand and its receptor. A lower dissociation constant (Kd) means the ligand stays bound more readily, so you need less of the ligand to occupy half the receptors. A higher association constant (Ka) indicates the complex forms more readily, again pointing to tighter binding. Since Ka and Kd are effectively reciprocal (Ka ≈ 1/Kd), lowering Kd and raising Ka both reflect tighter binding. That tighter binding is what we mean by higher affinity. Potency and efficacy involve additional factors beyond just affinity, and degradation rate isn’t a direct measure of binding strength.