Biology

The correct answer is: C.By increasing the number of cAMP molecules.

Explanation:

Signal transduction pathways can amplify a signal within a cell, even when only a small amount of ligand is present, through the use of second messengers like cAMP (cyclic adenosine monophosphate).

Once the ligand binds to the receptor, it activates a G-protein, which in turn activates an enzyme called adenylyl cyclase. This enzyme produces many molecules of cAMP from ATP. Each cAMP molecule can activate multiple protein kinases, which in turn can phosphorylate multiple target proteins, thus amplifying the original signal.

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