For each of the dialysis tubing treatments identify

3. For each of the dialysis tubing treatments, identify whether the solution inside was
hypotonic, hypertonic, or isotonic in comparison to the Beaker 1 solution.
Hypertonic
15% sucrose
Hypotonic
Your Choice #1
Your Choice #2
4. Did your weight-change calculations support your hypothesis and your predictions for each
dialysis bag? Why or why not?
5. From your results, which of your “unknown” solutions appears to contain more sugar
(among other unknown solutes)?
6. Do your “unknown” sugar solutions contain more or less sugar (among other unknown
solutes) than the 3%, 15% and 30% sucrose solutions? Why?
7. What characteristics of your “unknown” solutions besides sugar content might impact the
amount of swelling (or lack of swelling) in your dialysis bags containing these solutions?
How might this impact your conclusions about the amount of sugar present in your
“unknown”?
8. Cells exchange many substances with their environments using simple diffusion through the
lipid bilayer. Describe properties of the lipid bilayer and what properties block simple
diffusion (via passive transport). Why is simple diffusion through the lipid bilayer not
sufficient for all substances? Provide examples of two such substances.

BI205: Introductory Biology II Week 4 Lab Page 9 of 9
9. A concentration gradient affects the direction that solutes diffuse. Briefly describe how
molecules diffuse with respect to concentration.
10. What family of proteins facilitates the movement of water across the cell plasma membrane?
Briefly describe the structure of these proteins, and relate this structure to their function.