Microbiology MCAT Practice Question
During a bacterial infection, Vibrio cholerae secretes cholera toxin, an AB5 toxin that enters epithelial cells and catalyzes ADP-ribosylation of the Gs alpha subunit of heterotrimeric G proteins. This modification locks Gs in its active GTP-bound state. What is the direct molecular consequence of this constitutively active Gs signaling?
Answer choices
- ADecreased intracellular cAMP levels and reduced ion channel activation
- BConstitutive activation of adenylyl cyclase leading to excessive cAMP productionCorrect answer
- CInhibition of Na+/K+ ATPase pump function at the apical membrane
- DDirect blockade of tight junction proteins between epithelial cells
- EPrecipitation of actin filaments in the cytoskeleton
- FInhibition of phosphodiesterase enzymes preventing cAMP degradation
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.