Question

In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?

Answer 1

Since lactose functions as an inducer and binds to the repressor to render it inactive, adding lactose to the media activates the lac operon. Lactose is converted to glucose and galactose by forming β-galactosidase, which occurs when the lac operon system is activated. The repressor reactivates and the mechanism shuts down as soon as all of the lactose has been ingested.