During diffusion, when the concentration of molecules on both sides of a membrane is the same, the molecules will (1 point) move across the membrane to the outside of the cell. stop moving across the membrane.continue to move across the membrane in both directions. move across the membrane to the inside of the cell.ere are a couple of facts that'll help you out: Molecules tend to move toward the side where there is a LOWER concentration. A LOWER number of molecules. If the number of molecules is lower on the RIGHT side, then the molecules will tend to move toward the RIGHT. And the molecules NEVER stop moving.