ATP is a (+) allosteric effector, and CTP is a (-) allosteric effector of the enzyme ATCase. Both of these heterotropic effectors bind to the regulatory subunits on ATCase. The substrates of ATCase, aspartate and carbamoyl phosphate, bind the enzyme active site with positive cooperativity (i.e., they exert a “+” homotropic effect on activity). As the concentrations of the substrates change from values where [S] ≪ K_M to values where [S] is saturating ([S] ≫ K_M), how will the binding constants for each of the two allosteric effectors change? In other words, does ATP bind ATCase with higher affinity when [S] is low or high? Does CTP bind ATCase with higher affinity when [S] is low or high?