A student puts drops of Lugol’s iodine solution into the water in the beaker shown. The water turned red. After a short time, the starch solution inside the dialysis tubing turned black. Which function of the cell membrane was the student demonstrating? Facilitated diffusion of starch
Active transport of hydrogen ions.
Diffusion through a non-permeable membrane
Diffusion through a semi-permeable membrane

Diffusion through a semi-permeable membrane

Explanation:

A  membrane  that would only allow water, ions and certain molecules to pass through it by diffusion while restricting other large molecules molecules from passing through is called semi-permeable membrane

The iodine molecules were dissolved in the water in the beaker to form iodine solution.When the starch in the tubing was immersed into the red iodine solution, the molecules of iodine  diffuse across the tubing  walls which acts as the cells membrane -selectively permeable membrane to react with the starch solution. The reaction turns the starch blue black

The characteristic of the  cell membrane is due to the lipid bi-layer which allow certain substance pass through while restricting others because of the   inner hydrophobic (water hating)  and outer hydrophilic phospholipid layer. (water loving layer)These forms the double bi layer  to selectively control the movement of substances across it.