And if we combine these two curves we obtain the actual black curve that describes the S shaped, the Sigmoidal curve for this allosteric enzyme. And this is what we know as the concerted model. We have the all or nothing behavior in which we either exist in the T state in which the enzyme is inactivated or the art state in which the enzyme is fully active and basically carries out that particular catalytic reaction. Now, what about the two types of allosteric effectors that our cells actually use to basically control and regulate the activity of this enzyme? So let's begin by focusing on CTP. So remember, this enzyme catalyzes the first step in the biosynthetic process of CTP citadine triphosphate.