Question

A section of dialysis tubing is filled with a 40% starch solution (60% water). The tubing is then placed in a beaker containing of distilled water for 20 mins. a) What change would you expect to find in the mass of the dialysis tubing? b) Explain this change using appropiate terminolgy to describe the situation and type of transport

Answer 1

So if I recall correctly, the starch molecules are too big to go through the tiny pores of the dialysis tubing. The concentration of starch inside the tubing is greater than the concentration outside (essentially 0 outside the tubing). However, water molecules are small enough to fit through the pores of the tubing, and will tend to move inside the tubing to create an equal concentration on each side.

This process of water moving to higher concentrations of solute is a special type of diffusion called "osmosis".

Answer 2

someone said The water will move into the tubing making the inside of the tubing hypotonic. Water diffuses into the bag because the inside of the bag is hypertonic and water tends to move to an area with a higher concentration of molecule but im not sure is that is correct..i dont know what bag she is referring to

Answer 3

Yeah, that's essentially the same idea as I was saying. The hyper/hypotonicity stuff is just another way to describe what is happening during the osmosis process.

The bag that they are refering to is the dialysis tubing. They are essentially plastic bag with very tiny holes which let molecules under a certain size through. You can see pictures here: http://en.wikipedia.org/wiki/Dialysis_tubing

Basically inside the tubing/bag, is hypertonic, meaning that there is a greater concentration of solute (starch in this case) inside the bag. The outside is hypotonic of course (no starch = no solute). The osmosis process means that water will diffuse into the bag making it larger.

Answer 4

ohh okay thank you so much !