True or false? The mechanism by which glucose inhibits expression of the lac structural genes is known as catabolite stimulation, whereas the mechanism by which lactose stimulates expression of the lac structural genes is known as allosteric regulation. View Available Hint(s) True or false? The mechanism by which glucose inhibits expression of the lac structural genes is known as catabolite stimulation, whereas the mechanism by which lactose stimulates expression of the lac structural genes is known as allosteric regulation. True False

The repression of lac operon is mediated by the catabolite activator protein (CAP). The RNA polymerase can attach to promoter site, only when CAP combined with cAMP is available. Bacteria only accumulate cAMP only when starved. But when glucose is present, cAMP is not available and so CAP-cAMP is not formed. Hence the lac structural genes is turned off in the present of glucose.

Therefore the mechanism by which glucose inhibits the expression of the lac structural genes is by catabolite repression.

Whereas the process by which lactose stimulates the expression of lac operon is by derepression/allosteric regulation. Lactose binds to the lac repressor and deactivate it by causing it to change shape so it doesn't bind to the DNA