When a matrix molecule binds a surface receptor, which change happens next inside the cell?

1. Cells carry protein receptors on the extracellular surfaces of their plasma membranes. 2. A molecule within the matrix binds to such a receptor. 3. Binding changes the molecular structure of the receptor itself. 4. The receptor in turn changes the conformation of the microfilaments positioned just inside the plasma membrane. 5. Only after that do chemical signals travel on toward the nucleus. 6. DNA copying is not the immediate next event, so that answer skips several steps. 7. Calcium is stored by the smooth ER rather than released by the Golgi, so that answer misassigns the organelle. 8. The next change is a conformational change in the microfilaments. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 4 "Cell Structure", section 4.6 Connections between Cells and Cellular Activities_