Hormone X activates the cAMP second messenger system in its target cells. The greatest response by a target cell would come from applying a molecule of cAMP to the extracellular fluid surrounding the cell.
This is an intracellular second messenger molecule, which regulates activity of hormonal action.
the cAMP stands for cyclic adenosine monophosphate.
The molecules that transfer the signal received from the cell surface to the target hormone are called the second messenger molecules.
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