How is Glucose Involved in Catabolite Repression of the Lac

Question

How is glucose involved in catabolite repression of the lac operon?
A)Glucose causes cAMP levels to increase, which leads to increased CRP binding and the lac operon is activated even when lactose is present.
B)Glucose causes cAMP levels to decrease, which leads to decreased CRP binding and the lac operon is repressed even when lactose is present.
C)Glucose is also a substrate for β-galactosidase and thus competes with lactose for this enzyme.
D)Glucose activates transcription of the lacI gene to increase the amount of Lac repressor in the cell.

Accepted Answer

Glucose causes cAMP levels to decrease, which in turn leads to decreased CRP (cAMP receptor protein) binding to the lac operon. This results in repression of the lac operon even when lactose is present, as the CRP-cAMP complex is necessary for the activation of the operon.