Final answer:
Molecules will move along a concentration gradient across a semipermeable membrane until equilibrium is reached, after which there is no net movement of molecules in any direction.
Step-by-step explanation:
The molecule will continue to move along this semi-permeable concentration gradient across the semipermeable membrane until they reach equilibrium. Diffusion is the process where molecules move from an area of higher concentration to an area of lower concentration, and this movement continues until there is no longer a concentration gradient, meaning that molecules are distributed evenly. When equilibrium is achieved, molecules still move across the membrane, but the net movement in either direction is the same, indicating that equal amounts of the molecule are entering and leaving a cell, thereby stabilizing the system.