And what about in cell membranes? Is it the same case there? (Just need to quickly finish my practical report...lol).

usually it would be water molecules passing through the dialysis tubing as they are smaller than glucose molecules. It's a similar principle for cell membranes, only very small molecules (e.g. O2) can passively diffuse through the membrane, larger molecules will require ATP or some channels are specific to size or charge of the molecule (e.g. Na and K channels). Glucose would not diffuse through the membrane unassisted. Hope it helps a bit

It depends on the membrane (or rather what kind of channels are present). But a limiting factor is polarity. Glucose is very polar (or hydrophilic), as such it cannot pass a closed lipid membrane despite its relatively small size.

Ow and technically glucose can pass through a dialysis tube, because the MWCO is usually fairly large (~3k and up).

Edited February 24, 200916 yr by CharonY

I think we did an experiment like this in high school and found that glucose passed through the dialysis membrane quite easily. I don't know any specifics on the characteristics of the particular dialysis membrane we used though.

Just wanted to add: MWCO = molecular weight cut-off.