Answer:
D
Explanation:
Hormones are bigger than the cell pores hence cannot pass through the cell membrane to influence biochemical processes. Therefore, hormones (such as glucagon and insulin) bind onto receptors on the cell membrane, then transmembrane proteins, such as the G-protein, change conformation activating the secondary messengers inside of the cell. Cyclic- AMP is a major secondary messenger significant in activating protein kinases.
