[Campbell Biology P.274] If a cell is exposed to a ligand that binds to a receptor and conse... | Practice Question

If a cell is exposed to a ligand that binds to a receptor and consequently leads to the activation of phospholipase C, which of the following immediate effects would be observed regarding calcium ion Ca2+ concentration in the cytosol?

  • A: The Ca2+ concentration in the cytosol would decrease due to increased pumping into the ER.
  • B: The Ca2+ concentration in the cytosol would remain unchanged as phospholipase C only affects DAG.
  • C: The Ca2+ concentration in the cytosol would increase due to the opening of IP3-gated calcium channels in the ER membrane.
  • D: The Ca2+ concentration in the cytosol would increase due to increased Ca2+ influx from the extracellular fluid.
  • E: The Ca2+ concentration in the cytosol would decrease due to increased uptake by mitochondria.

Explanation

Phospholipase C cleaves PIP2 into IP3 and DAG. IP3 then diffuses to the ER membrane and binds to IP3-gated calcium channels, causing them to open. This allows Ca2+ to flow out of the ER, down its concentration gradient, into the cytosol, thereby increasing cytosolic Ca2+ concentration.