When both lactose and glucose are available to E.coli,which part of the lac operon regulation assures that glucose will be metabolized first? A)CAP binds to cAMP and then to the promoter only in the presence of low glucose. B)The repressor cannot bind to the operator in the presence of lactose. C)Permease allows lactose to enter the cell when lactose enters the cell. D)The repressor binds to the operator in the absence of lactose. E)RNA polymerase transcribes the lac operon to make a single RNA molecule.

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CAP (catabolite activator protein) binds to cAMP (cyclic AMP) and then to the promoter of the lac operon, increasing transcription of the genes involved in lactose metabolism. However, CAP is only activated when glucose levels are low and cAMP levels are high. Therefore, when glucose is present, CAP is inactive, and lactose metabolism is not a priority. Glucose is metabolized first due to its higher energy yield compared to lactose.

When Both Lactose and Glucose Are Available to E