Alternatove to Egg Membrane prac

[linotas]

Hi All,

We have a student that is ana to egg. Teacher wanted to do the prac where you dissolve the shell of an egg and show the finction of the membrane. This teacher is a PHD Chemist, so knows nothing about bio. Any thoughts on an alternative using dialysis membrane? From what I can get out of him, its for yr 8 to demonstrate a membrane and its functions.

[RosalieM]

do a search on here for digestion prac I think. There's been mention of zip lock bags that work but at our school we use dialysis tubing. set up 2 beakers. Cut 2 lenths of dialysis tubing about 15cm each. Tie one end of each really tight with string so liquid can't escape. Fill one with a start solution (I find sending out syringes helps the kids fill them with little mess) and the other with a strong glucose solution. Tie the tops and wash them and check for leaks. Place in a beaker of water each so they are covered. In the starch beaker put a few squirts of iodine into the water and with the glucose one squirt in some benedicts solution. Leave for a few days. The dialysis tubing acts as a membrane and the iodine can get in but the starch can't get out so you have a, expanded black tube. The glucose can get out but the benedicts can't get in so you end up with yellow outside and a clear tube that has shrunk.

[mazza]

Hi,

Instead of using dialysis tubing, small freezer bags can be used
much cheaper and just as effective!

[Narelle01]

Yes, for year 8, def use freezer bags, the work within 30 mins.

Only snrs get dialysis tubing here now. I think the freezer bags are 80 cents a packet, dialysis tubing is over $50!!