Final answer:
Polarity, solubility, and size determine how a regulatory molecule influences its target cell.
Step-by-step explanation:
The regulatory molecule's ability to influence its target cell is determined by its polarity, solubility, and size. Polarity refers to the presence of a positive or negative charge, solubility refers to the ability to dissolve in a certain solvent, and size refers to the molecular size of the molecule. For example, a regulatory molecule with a positive polarity may bind to a receptor on the target cell's membrane, triggering a response. A water-soluble regulatory molecule may bind to a receptor on the cell surface, while lipid-soluble molecules can penetrate the cell membrane and directly influence gene expression.