Glucose
A) is preferentially used over lactose in E. coli as a result of catabolite repression AND levels are correlated with cAMP levels.
B) is preferentially used over sucrose in E. coli as a result of catabolite repression AND levels are directly sensed via catabolite repression.
C) is preferentially used over lactose in E. coli as a result of catabolite repression AND glucose levels are the inverse of cAMP levels.
D) is preferentially used over lactose in E. coli as a result of catabolite repression AND levels directly affect the production of lactose dehydrogenase.
E) is preferentially used over sucrose in E. coli as a result of catabolite repression AND levels are correlated with cAMP levels.

Question

Glucose
A) is preferentially used over lactose in E. coli as a result of catabolite repression AND levels are correlated with cAMP levels.
B) is preferentially used over sucrose in E. coli as a result of catabolite repression AND levels are directly sensed via catabolite repression.
C) is preferentially used over lactose in E. coli as a result of catabolite repression AND glucose levels are the inverse of cAMP levels.
D) is preferentially used over lactose in E. coli as a result of catabolite repression AND levels directly affect the production of lactose dehydrogenase.
E) is preferentially used over sucrose in E. coli as a result of catabolite repression AND levels are correlated with cAMP levels.

Quizplus · Accepted Answer

Glucose is preferentially used over lactose in E. coli as a result of catabolite repression, where glucose represses the lac operon that is responsible for lactose utilization. Glucose levels are regulated by the inverse relationship of cAMP levels via the cAMP-CRP complex. When glucose is high, cAMP is low, which leads to the repression of the lac operon. Therefore, choice C is the best answer.