[Campbell Biology P.266] A pharmaceutical company synthesizes a novel molecule that perfectl... | Practice Question

A pharmaceutical company synthesizes a novel molecule that perfectly fits into the binding site of a specific plasma membrane receptor, but this molecule does not induce the receptor's shape change. If this molecule is introduced into a cell system, what would be the most likely immediate effect on the cellular response to the natural ligand?

  • A: The receptor would undergo an unintended conformational change, activating a different signaling pathway.
  • B: The natural ligand's binding would be enhanced, leading to an amplified cellular response.
  • C: The cell's normal response to its natural ligand via that specific receptor would be inhibited or blocked.
  • D: The novel molecule would directly activate intracellular signaling pathways without receptor involvement.

Explanation

The text explains that ligand binding generally causes a receptor protein to undergo a change in shape, which is crucial for activating the receptor and subsequent cellular events. If a molecule binds to the receptor's site but does not induce this shape change , it would block the natural ligand from binding without initiating a response, thus inhibiting or blocking the normal cellular response.