Second messengers Original Scenario-Based Download PDF

Questions

1. 1.

   In an astrobiology experiment, researchers engineer an abyssal biosensor cell named Luminovore that flashes brightly upon detecting extracellular chemical plumes at hydrothermal vents. When a signaling molecule binds to a receptor on the outer membrane of Luminovore, the ligand remains outside the cell, yet thousands of metabolic enzymes deep inside the cytoplasm are activated almost simultaneously within milliseconds. Biochemical analysis reveals that this rapid, cell-wide response is mediated by an immediate surge of cyclic AMP throughout the interior fluid. Which statement best explains why cyclic AMP functions effectively as a second messenger in this communication system?

   • A) It is a small, non-protein molecule that diffuses rapidly through the cytosol to amplify and relay the signal to intracellular targets.
   • B) It functions as a transmembrane receptor that directly captures extracellular ligands and phosphorylates nuclear targets.
   • C) It is a structural scaffolding protein that permanently anchors cytosolic enzymes to the outer cell membrane.
   • D) It hydrolyzes all intracellular energy reserves to terminate transduction cascades before downstream kinases can activate.