Diffusion through a membrane?

Question

Can someone explain to me an example of the Dialysis Tube membrane? -( the starch, glucose, indicator).

Diffusion through the membrane - onion cell membrane?

Answer 1

Don't know exactly how your experiment was set up.  The dialysis tubing is a type of selectively semipermeable membrane.  Water can pass through it freely, as can some smaller molecules like salt.  Starch is too big to pass through.  The water goes back and forth across the membrane TOWARDS the greater concentration of solute.  The indicator is usually iodine, which reacts to form a blue color with starch, just letting you know where the starch is present.  See the site below for one common way to run this experiment.

The cell membrane is also a selectively semipermeable membrane, so it acts similar to the dialysis tubing (but other transport mechanisms are possible with cell membranes, not just diffusion.)

Good luck.