Final answer:
Water-soluble hormones bind to receptors on the outer surface of the cell membrane, while lipid-soluble hormones can enter the cell and interact with intracellular receptors to regulate gene transcription and cell activities.
Step-by-step explanation:
The main difference between water-soluble and lipid-soluble hormones lies in their ability to enter cells. Water-soluble hormones, such as amino acid-derived and polypeptide hormones, cannot diffuse through the plasma membrane. Instead, they bind to receptors on the outer surface of the membrane, triggering a signaling pathway. On the other hand, lipid-soluble hormones, like steroid hormones, can permeate the plasma membrane and enter the cell, where they interact with intracellular receptors to regulate gene transcription and long-term cell activities.