How is Glucose Involved in the Catabolite Repression of the Lactose

Question

How is glucose involved in the catabolite repression of the lactose operon?
A) It has nothing to do with regulation of the lactose operon.
B) It results in decreased cAMP levels,which in turn leads to decreased CRP binding;thus the lac operon is repressed even if lactose is present along with the glucose.
C) It is also a substrate for β-galactosidase and thus competes with lactose for this enzyme.
D) Its presence in the cell increases the amount of lac repressor in the cell.
E) It provides energy to the operon.

Accepted Answer

Glucose is involved in the catabolite repression of the lactose operon by decreasing cAMP levels, which leads to decreased CRP binding. This results in the repression of the lac operon even if lactose is present. Glucose and other preferred carbon sources are utilized before lactose, and this regulation ensures energy efficiency for the cell. Glucose does not compete with lactose for β-galactosidase and does not increase the amount of lac repressor in the cell.