Changes in signal transduction and disease Transitional Reasoning Download PDF

Questions

1. 1.

   In individuals infected with Vibrio cholerae, cholera toxin chemically modifies the alpha subunit of a stimulatory G protein in intestinal epithelial cells, preventing it from hydrolyzing bound GTP into GDP. This molecular alteration permanently disrupts the normal off-switch of the signaling pathway. Which cellular outcome directly results from this altered signal transduction mechanism to cause severe dehydration?

   • A) Adenylyl cyclase is permanently deactivated, resulting in an abrupt depletion of intracellular cAMP and defective ion transport.
   • B) Adenylyl cyclase remains constitutively active, causing sustained high cAMP levels that continuously drive chloride and water secretion.
   • C) Cell-surface receptors are rapidly degraded, preventing signaling molecules from triggering second messenger cascades.
   • D) Phospholipase C is continually suppressed, blocking the cleavage of membrane phospholipids into inositol trisphosphate.