A solution containing proteins of a particular type is exposed to the same concentrations of ligands X and Y,but the percent saturation of molecule X is greater than the percent saturation of molecule Y.Which is most likely to be a true statement?
A)The binding sites for ligand X are 100% saturated.
B)The binding sites for ligand X have greater specificity than the binding site for ligand Y.
C)Ligand X must be a competitive inhibitor of ligand Y.
D)Both ligands must bind to the same binding site on the protein.
E)The protein has a higher affinity for ligand X than for ligand Y.

Question

A solution containing proteins of a particular type is exposed to the same concentrations of ligands X and Y,but the percent saturation of molecule X is greater than the percent saturation of molecule Y.Which is most likely to be a true statement?
A)The binding sites for ligand X are 100% saturated.
B)The binding sites for ligand X have greater specificity than the binding site for ligand Y. 
C)Ligand X must be a competitive inhibitor of ligand Y.
D)Both ligands must bind to the same binding site on the protein.
E)The protein has a higher affinity for ligand X than for ligand Y.

Quizplus · Accepted Answer

The fact that the percent saturation of molecule X is greater than molecule Y implies that the protein has a higher affinity for ligand X than ligand Y. Therefore, choice E is the best answer. Choice A is contradicted by the fact that the percent saturation of molecule Y is not at 100%. Choice B is not necessarily true given the incomplete information. Choice C cannot be inferred without additional information. Choice D is unlikely since it is uncommon for two ligands to bind to the same specific site with differing affinity.

A Solution Containing Proteins of a Particular Type Is Exposed to the Same