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+-------------+      +----------------+      +-------------+
| Extracellular | ---> | G protein-coupled | ---> | Adenylate   |
| Signaling    |      | Receptor (GPCR)  |      | Cyclase     |
| Molecule     |      +----------------+      +-------------+
+-------------+               |                        |
                              |                        |
                              v                        v
                    +----------------+          +----------------+
                    | G protein (Gαβγ) |          | Adenosine      |
                    +----------------+          | Triphosphate    |
                              |                  | (ATP)           |
                              |                  +----------------+
                              v                        |
                    +----------------+                  |
                    | Adenylate      |                  |
                    | Cyclase        |                  |
                    +----------------+                  |
                              |                        |
                              v                        |
                    +----------------+                  |
                    | cAMP           | <----------------+
                    | Second Messenger|
                    +----------------+