What is stimulated by the placing of the dialysis tubing in rice

Dialysis tubing simulated a cell membrane that leads to entering of micromolecules.

Dialysis tubing simulated a cell membrane which is permeable to small molecules means allows to enter small molecules such as oxygen, glucose and water molecules etc but not to larger molecules to enter the cell due to its large size and the holes in the cell membrane are smaller. Due to small size of materials or molecules, they can easily enter inside and comes outside  because the size of the hole is bigger than their size so that's why it is concluded that micromolecules are stimulated by the placing of the dialysis tubing in rice.