Combine your understanding of ATP conversion and PKA activation to explain how cyclic AMP acts as a secondary messenger in the signaling pathway.

• A. Cyclic AMP directly binds to the GPCR to initiate the signaling pathway.
• B. Cyclic AMP inhibits adenylate cyclase to prevent further ATP conversion.
• C. Cyclic AMP activates protein kinase A, which then phosphorylates target proteins to elicit cellular responses.
• D. Cyclic AMP is converted back to ATP to sustain the signaling cycle.

Answer: (C)