AP Biology
Name_________________________________
Cell Processes Lab
Mr. Hubert
Date_________________ Block____________
Purpose: To determine how plant cells are affected by solutions of water of varying purity. We will be placing known
masses of potato samples in distilled water (pure), 5% saline and 10% saline solutions.
1. Problem/question: What will happen to the mass of potatoes when placed in the various solutions?
2. Research: reflect back on your notes and the textbook regarding diffusion and osmosis....prior to making a
prediction, discuss this issue with your lab partner and develop a possible explanation as to what you believe will
happen to the mass of three different potato samples when placed into the three different solutions.
3. Prediction/hypothesis: Carefully read through the procedure.
What do you believe will happen to the three potato samples when placed in the three different solutions? This
should be written as an "if then statement".
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4. Procedure:
a. Acquire three samples of potato tissue (four cores of equal length)
b. Weigh and record the initial mass of each sample in data table 1 below
c. Place each sample in the appropriate marked solution for 30 minutes.
d. Remove the potato samples from their respective solutions.
e. Using a paper towel, gently blot the samples dry and record their final mass in data table 1
f. Calculate the change in mass and the % change (+ or -) in data table 1
(data table 1)
Distilled 2%
10%
% gain or loss= change in mass/initial mass *100
water
solution solution
Final Mass (g)
example:
+2g/8g= .25 *100 = +25%
Initial Mass (g)
Change in mass (g)
% gain or loss
(be sure to include the sign + or -)
The plus sign (+) means that the potatoes gained
mass!
If they lost mass, the change would be negative.
5. Constants and Variables:
a. List four constants in your procedure? ________________________________________________________
b. Identify the dependent variable (the measured factor): __________________________________________
c. Identify the independent variable (the manipulated factor) _________________________________________
g. Results:
 Create a bar graph with % gain or loss on the Y axis and the different solutions on the x axis below:
% GAIN
0%
% LOSS
Distilled
2%
10%
Water
h. Analysis: Write a statement which describes what happened to the potato cells based on your
interpretation of the data table, your graph and your understanding of diffusion and osmosis
5.
Conclusion: (restate your hypothesis) Write a statement supporting your hypothesis or a statement rejecting
your hypothesis:
--------------------------------------------------------------------------------------------Questions:
a. Which cell sample lost the most mass? _______________ Why do you think this happened?
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b. Gently bend each of your samples and take notice of which sample seems to be the most rigid. Which
sample seems
to be the most rigid? ________________________ Why do you think this sample is more rigid than the other
samples?
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c. This rigidness, or crispness is due to turgor pressure..........adjacent plant cells exerting pressure on one
another as their cell walls bulge. OK, now that you know about TURGOR pressure.............how would you
prepare carrot and celery sticks for friends so that they are as crisp as they could possibly be?
d. Why is it that animal cells cannot develop turgor pressure?