I just missed what she said about GTP and kInase. I heard that GTP is a second messenger and kinases phosphorylate second messengers. What else do I need to know? How does the message get to GTP?
The important thing to know about cell signaling is that a chain reaction occurs between molecules after the ligand binds to the protein. Those intermediary molecules are second messengers, sending messages to other second messengers (like GTP) to get them to start their role. Phosphorylating second messengers activates them.