Put the steps of the process of signal transduction in the order they occur. 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released. (A) 1, 2, 3, 4, 5 (B) 3, 1, 2, 4, 5 (C) 3, 1, 5, 2, 4 (D) 1, 2, 5, 3, 4