Signal transduction pathways Original Scenario-Based Practice

Questions

1. 1.

   A team of astrobiologists studying the subterranean organism Cryofrigus chemilux identifies a multistep phosphorylation cascade that triggers bioluminescence: an activated membrane receptor activates Kinase A, which activates Kinase B, which subsequently activates Kinase C to stimulate light-producing enzymes. In a laboratory strain, researchers introduce a loss-of-function mutation in the specific protein phosphatase responsible for dephosphorylating Kinase B. Which outcome would most likely occur when this mutant strain is exposed to a brief pulse of the signaling ligand?

   • A) The organism fails to initiate the cascade because Kinase B cannot accept phosphate groups without active phosphatase priming.
   • B) The pathway exhibits prolonged and unattenuated activation of Kinase C, persisting even after the ligand has dissociated from the receptor.
   • C) Phosphorylation of Kinase C is blocked because phosphate groups must be passed directly from Kinase B to Kinase C via phosphatase activity.
   • D) Signal amplification decreases sharply because protein phosphatases are required to transfer high-energy electrons through the cascade.

Answers and step-by-step solutions appear after you finish the test.