Signal transduction pathways Transitional Reasoning Download PDF

Questions

1. 1.

   Researchers investigating a growth-factor signaling cascade treat cultured mammalian cells with a pharmacological compound that selectively inhibits intracellular protein phosphatases. When these treated cells receive a brief pulse of the signaling molecule, downstream target gene expression continues for hours longer than in untreated control cells. Based on the mechanism of signal transduction pathways, which statement best explains this prolonged response?

   • A) The compound prevents the extracellular signaling molecule from detaching from its cell-surface receptor.
   • B) Target proteins remain functionally active because the removal of activating phosphate groups is impaired.
   • C) The inhibition causes the pathway to bypass protein kinases entirely and rely exclusively on lipid-soluble second messengers.
   • D) Membrane receptor tyrosine kinases are locked into an unphosphorylated monomeric state that continually generates signals.