Final answer:
Low levels of glucose in bacterial cells result in increased levels of cAMP, which binds to the CAP protein, enhancing the transcription of the lac operon. This results in increased levels of enzymes necessary for the metabolism of lactose. The exception is that the CAP-cAMP complex does not lose its affinity for DNA.
Step-by-step explanation:
The lac operon is a group of genes that are involved in the metabolism of lactose in bacterial cells like Escherichia coli. When glucose levels are low, the cell metabolizes other sugars, such as lactose, if they are available.
The utilization of lactose is facilitated by the lac operon which is activated under these conditions.
- cAMP levels increase because as glucose levels drop, adenylyl cyclase converts ATP to cAMP, thus increasing its concentration in the cell.
- permease levels increase because the lac operon genes coding for lactose permease are transcribed, allowing more lactose to enter the cell.
- Beta-galactosidase levels increase as this enzyme, which is responsible for the hydrolysis of lactose into glucose and galactose, is produced in greater amounts.
- lac operon is activated since cAMP binds to the CAP protein, which then binds to the promoter region of the lac operon, increasing transcription.
The CAP-cAMP complex does not lose its affinity to DNA in response to low glucose; rather, cAMP binds to CAP, and this complex has a higher affinity for the promoter region of the lac operon, facilitating transcription.
Therefore, the correct answer is E. CAP-cAMP loses its affinity to DNA, which is the statement that does not occur when glucose levels are low.