Insulin operates by activating a receptor on the outside of the target cell. Based on your knowledge of hormone types, do you expect insulin to be an amino acid-based hormone or a steroid hormone, and why?

• A. Amino acid-based because it cannot pass through the cell membrane of the target cell.
• B. Steroid because it cannot pass through the cell membrane of the target cell.
• C. Amino acid-based because it is not water-soluble.
• D. Steroid because it is water-soluble.