Answer: The solute molecules were too big to fit through the wrong shape.
Explanation: The solute particles were unable to go in and out of the cell because of the principal guiding the process of Osmosis and the cell membrane of the biological cell. Osmosis prevents the solute particles from leaving the cell but rather permits the movement of solvent from the region of higher solute concentration to the region of lower solute concentration in other to achieve a state of equilibrium in the biological cell.
The cell membrane is made up of semi permeable membrane which is a type of membrane that allows certain types of molecules to pass through it. Therefore the solute molecules couldn't pass through the cell membrane because the semi permeable membrane has a different/ odd shape that restricts it's smooth passage. I hope this helps, thanks.