How is dialysis tubing a good model for a cell membrane and a bad model?

Question

My 8th grade bio class created a model of a cell membrane using dialysis tubing. We filled it with a stock solution of sugar,salt,water,and starch. We placed it in a beaker of distilled water. After 20 mins. we tested the beaker solution for traces of the stock solution. The tests showed that the cell membrane let everything diffuse but the starch. Now i understand why this all happens I'm just struggling on how dialysis tubing is a good model for a cell membrane , and a bad one. Any help would be appreciated!

Answer 1

Dialysis tubing is a good model for a cell membrane because it is selectively permeable - allowing some materials to pass through and not allowing others through.

It's not just like a cell membrane because the cell membrane has some other tricks to get materials to go through:
-- facilitated transport through special proteins
-- active transport using special proteins to move materials from low concentration to high concentration
-- bulk transport to move larger particles or liquid by endocytosis or exocytosis

Answer 2

1

Answer 3

Dialysis Tubing

Answer 4

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Like a cell membrane, dialysis tubing has a semi-permeable membrane (only small molecules can go through the lining). Therefore, this mimics the cell membrane when it comes to diffusion (movement of solutes) and osmosis (movement of water)

Answer 5

Dialysis tubing is semipermeable as of cell membrane.

Answer 6

ah. I did this in my class as well. the dialysis tubing acts as a selectively permeable membrane, letting only certain substances through. the starch molecules are too big to pass through the pores of the bag.

it is not the best model though, because it does not account for receptors on the cell membrane or transmembrane proteins, and cannot pump protons across the membrane in a proton gradient. active and passive transport cannot be represented.