Question

Question 1 (1 point) Vasoconstriction occurs when epinephrine (adrenaline) binds to the a-adrenergic receptor on vascular smooth muscle cells. One way to treat high blood pressure is to administer competitive inhibitors that bind to this receptor. The Kd for binding of epinephrine to this receptor is ~UM. Based on the measured affinity (Kd) of the following drugs for the a-adrenergic receptor, which might be good candidates for high blood pressure medication? Drug A: Kd = 0.6 M; Drug B: Kd = 6 nM; Drug C: Kd = 6 UM; Drug D: Kd = 60 uM; Drug E: Kd = 60 mm None of the drugs have a dissociation constant equal to that of epinephrine, therefore, none of these drugs would be good competitive inhibitors. Only Drug C has a dissociation constant close to that of epinephrine, therefore it is the only one that is a good candidate for competitive inhibition. It is the association rate, not the dissociation constant that determines the effectiveness of a competitive inhibitor, therefore, these data do not indicate which might be good competitive inhibitors. O Drugs C, D, and E all have a Kd higher than that of epinephrine, therefore they will bind the receptor with a higher affinity and might be good competitive inhibitors. Both Drugs A and B have a kd lower than that of epinephrine, therefore, they will bind the receptor with a higher affinity and might be good competitive inhibitors. D

Answer 1

Answer 1: Dissociation contant (Kd) is a type of equilibrium constant that mesaures how well a larger heterogeneous molecule separtes into smaller components. It is the inverse of the association constant. Smaller is the dissociation constant, hihger is the affinity between the ligand and the protein.

The most correct answer is option 2: only drug C has a dissociation constant close to that of epinephrine, therefore is the only that is a good candidate for competitive inhibition.

Option 1 is incorrect because, although the dissociation constant is nto equal to that of epinephrine, binding will occur for near close or lower Kd. It cannot be said that none of the drug will be a competitive inhibitor.

Option 3 is incorrect because, only dissociation constant single handedly can determine the affinity of a ligand and protein molecules.

Option 4 is incorrect becuase, higher the value of Kd than that of epinephrine, lower is the affinity and is therefore not a good competitive inhibitor.

Option 5 is incorrect because, the Kd value of only Drug B is lower than that of epinephrine not Drug A.