Select all of the following answers about allosteric control of enzymatic activity that are true.
a) allosteric effectors give rise to sigmoidal vo vs. [s] kinetic plots.
b) binding of the effector changes the conformation of the enzyme molecule.
c) an effector may either inhibit or activate an enzyme.
d) heterotropic allosteric effectors compete with substrate for binding sites.

A) Allosteric effectors give rise to sigmoidal Vo vs. [S] kinetic plots. .

B) Binding of the effector changes the conformation of the enzyme molecule.

C) An effector may either inhibit or activate an enzyme.

Explanation:

Allosteric enzymes are the ones in which binding of a modulator or effector to one site on the enzyme alters the binding properties of another site on the same enzyme.

Here, the binding of effector may convert the allosteric enzyme into a more-active or less-active form. Therefore, an effector may be inhibitory or stimulatory to the activity of allosteric enzymes.

The allosteric enzymes exhibit a sigmoidal curve in Vo vs [S] kinetic plots which in turn is the characteristic feature of cooperative binding. These enzymes do not follow the hyperbolic Michaelis- Menten relationship.

For the binding of a positive effector, the sigmoidal curve represents a transition of the enzyme from a low affinity to a high-affinity state.