Epinephrine is a protein hormone found in many animals. Epinephrine stimulates a signaling pathway that results in the breakdown of glycogen to glucose in the liver cells. Which of the following describes the initial steps in the process whereby epinephrine stimulates glycogen breakdown?

After a signal (ligand) binds to a receptor, a series of steps occur prior to a response. The signaling pathways may involve many proteins and second messengers in the cell.

Cell surface receptors help relay a message, but usually do not directly participate in the response.

Signaling molecules are often large and do not diffuse into cells.

Similarly, signaling molecules are not taken into the cells through endocytosis.