Final answer:
The statement about CRP activating the arabinose operon in the presence of cAMP is false. CAP/CRP, when bound to cAMP, regulates the lac operon by promoting RNA polymerase binding and transcription, whereas arabinose operon is regulated by AraC in the presence of arabinose.
Step-by-step explanation:
In the regulation of the arabinose operon, it is false that CRP activates expression when bound to cAMP. The catabolic activator protein (CAP), also known as CAMP receptor protein (CRP), becomes an active complex when it binds to cAMP. This complex primarily regulates the lac operon, not the arabinose operon. In the context of the lac operon, when glucose levels are low, cAMP levels increase. This increase in cAMP leads to the formation of the cAMP-CAP complex which binds to the promoter region of the operon. The binding enhances the ability of RNA polymerase to bind to the promoter region, thus initiating the transcription of the operon's related genes. However, the arabinose operon is regulated by the AraC protein. When arabinose is present, it binds to AraC, and this complex then binds to the initiator site of the arabinose operon to promote transcription.