Positive and negative feedback Transitional Reasoning Practice

Questions

1. 1.

   In an epithelial cell signaling pathway that regulates cell division, binding of a growth factor to its receptor activates an intracellular cascade culminating in the activation of Kinase Z. Active Kinase Z then phosphorylates and inactivates an upstream pathway scaffold protein, leading to rapid signal dampening. If a mutation prevents Kinase Z from binding to and phosphorylating this scaffold protein, which type of regulatory mechanism is disrupted, and how will the cell respond upon growth factor stimulation?

   • A) Negative feedback regulation is disrupted, resulting in prolonged and unattenuated signaling downstream of the receptor.
   • B) Positive feedback regulation is disrupted, resulting in failure to initiate the intracellular cascade upon ligand binding.
   • C) Negative feedback regulation is disrupted, resulting in the immediate irreversible degradation of Kinase Z.
   • D) Positive feedback regulation is disrupted, resulting in premature termination of the signal before Kinase Z can become active.

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