Compare two ways that the binding of a signal molecule to a receptor protein causes a change in the activity of the receiving cell

Cell signalling is a process by which cells communicate with each other and transfer messages. When a signal molecule binds to a receptor protein, changes occur in the receptor proteins. Two changes are listed below:
1. The receptor protein undergoes conformational changes and acts as an enzyme.
2. The receptor protein that makes a second messenger molecule that leads the reaction further to other cells or molecules.

The answer to that question is a