Expert: Walter Hintz - 10/23/2008

Question
I have a lab write-up. it's about the hypertonic a and hypotonic lab. we used potato cut it in same length and put into 11 different concentration test tube. here is the data table:
test tube #    concentration of sucrose solution (mol/L)
1              1.0
2              0.9
3              0.8
4              0.7
5              0.6
6              0.5
7              0.4
8              0.3
9              0.2
10             0.1
11             0
and the following data is my potato percentage in mass and volume
tube       mass        volume
1          -39.0       -42.9
2          -37.5       -45.5
3          -37.5       -39.1
4          -28.0       -33.3
5          -26.9       -33.3
6          -16.7       -25.0
7          -14.8       -16.7
8          -4.0        -26.7
9          0           0
10         0           0
11         12.5        4.1

those are my data.
and there are some questions that i have to figure out...
i wonder could you help me...
1. what was the purpose of using distilled water as a solution in this exercise?
2. when chemicals are added into the human body intravenously (directly into the bloodstream), they are added in solution. why is it important that this solution be of the same concentration as that of blood plasma (liquid portion of the blood)?
3. in order to keep vegetables "crisp", grocery stores use cool water or ice. Which would keep vegetables crisper, tap water or distilled water? Explain.
4. From this exercise, what can you conclude about the permeability of potato cytoplasm with respect to sucrose and water molecules?
5. If potato cells were suspended in a 1.0 mol/L sucrose solution, what would you expect to happen to the mass of the potato cells? Explain.
6. Which solutions (if any) were hypertonic, isotonic, or hypotonic to the potato? Explain how you know.
7. In terms of tonicity, explain why some potato sections increased in mass, why some decreased in mass, why some changed very little in mass.
8. In this experiment, why was it important that the potato cores were the same length? ## is that because of the surface??

those are the questions that i have to do. and i also need to write some conclusions, i wonder could you give me head for doing this. thanks so much!!!

Answer
All of these questions involve osmosis'
1. Distilled water is used so the desired salt concentration can be maintained
2 Saline solution (0.09 is given in IVs. It has to be isotonic (same concentration as body fluids or person dehydtates
3. distilled
4.water moves in and out but sugar does not
5.it would be less
6. If they potato lost water it was hypotonic
7.If mass was lost solution was hypotonic :If amss increased solution was hepertonic an dif it stayed the same it was isotonic
8.the same length acted as a control