In relation to receptor affinity, which statement is true about Ka values?

In relation to receptor affinity, which statement is true about Ka values?

• A. Lower Ka values indicate lower affinity.
• B. Higher Ka values correspond to higher affinity.
• C. Ka does not relate to affinity.
• D. Ka relates to efficacy.

Answer: (B)

Affinity is about how tightly a ligand binds to its receptor. The association constant Ka captures this tendency: a larger Ka means the bound complex is favored, so more receptor–ligand complexes form at equilibrium. Since Ka = 1/Kd, a high Ka corresponds to a low dissociation constant Kd, which is another way of saying high affinity. Efficacy, on the other hand, concerns the maximal response once the receptor is activated, not how well the ligand binds. So the statement that higher Ka values correspond to higher affinity is correct because Ka directly reflects how readily the ligand associates with the receptor, with larger values indicating tighter binding.

Affinity is about how tightly a ligand binds to its receptor. The association constant Ka captures this tendency: a larger Ka means the bound complex is favored, so more receptor–ligand complexes form at equilibrium. Since Ka = 1/Kd, a high Ka corresponds to a low dissociation constant Kd, which is another way of saying high affinity. Efficacy, on the other hand, concerns the maximal response once the receptor is activated, not how well the ligand binds. So the statement that higher Ka values correspond to higher affinity is correct because Ka directly reflects how readily the ligand associates with the receptor, with larger values indicating tighter binding.