Diffusion and Osmosis Lab Report pg.1
Investigation 4: Diffusion and Osmosis Lab
Report
Diffusion, Osmosis,
and How They Apply to
Membrane
PermeabilityHADEEL
by Hadeel Haidar
AP Biology, Harrison
November, 2013
Lab Partners:
Jason Lin
Ahmad Ghaida
Tabytha Dillinder
Audrey White
Special thanks to Fatima, Errick,
Moustafa, Khalid, Jordan, Hafsa,
Hanna, Tyler, and Bob.
ABSTRACT
The main course of this lab was correlating energies to main biological processes that living organisms
deal with on a 24/7 basis. Throughout the lab, it has been hypothesized that the weight of a cell
increases with one combination of substances inside and out, then the weight of the cell will decrease
with the reverse combination, if the mass of a potato decreases, then the solution most have a sucrose
concentration higher than that of the potato, and if a cell has a smaller volume, then it will diffuse quicker
and more efficiently.
INTRODUCTION
Energy exists all around us; it is neither destroyed or created, and without it, biological
processes would not be able to occur. The two main types of energy that play a key role in these
processes are kinetic energy and potential energy. Kinetic energy is energy an object produces when in
motion. Potential energy is energy which results from position or configuration. Some environmental
factors that affect kinetic energy are the size of the molecule, the nature of the material that the molecules
are moving through, the charges on the molecule, and whether they’re in a hypotonic, hypertonic, or
isotonic solution. These factors affect diffusion rates in that an increase in temperature speeds up
movement across a membrane. Also, large molecules need energy and transport protein to transport
molecules across a membrane. Gradients are important in diffusion and osmosis because they generally
occur as passive transport moving from a high to a low concentration. A main effect on the process of
osmosis is the resistance to water movement in the cell by the cell wall. It has been hypothesized that the
weight of a cell increases with one combination of substances inside and out, then the weight of the cell
will decrease with the reverse combination, if the mass of a potato decreases, then the solution most
have a sucrose concentration higher than that of the potato, and if a cell has a smaller volume, then it will
diffuse quicker and more efficiently.
METHODS
Procedure 1: Surface Area and Cell Size
Materials:
2% Agar containing NaOH and phenolphthalein Metric Rulers
1,000ml Beaker
Box Blade Cutter
250ml of HCl
Stopwatch
Watch Glass
Paper towel
Upon entering the lab, safety precautions were taken into account through the use of safety
goggles. Failure to abide by these safety precautions would result in the harm of the person performing
the experiment. Materials should be kept in the lab, washed, cleaned, and put away following the end of
use. These materials may not leave the lab in that they would be misused. 2% Agar, containing NaOH
and phenolphthalein, was provided by the lab instructor. Using a metric ruler and a box cutter, three
cubes of agar proceeded to be cut.
The first, and biggest, piece was cut to have a 4 cm side length all the way around. The second
piece of agar was cut to have a 3 cm side length. The final square to be cut had a 2 cm side length. A
metric ruler was used to measure the agar prior to the incision. A box cutter blade was used to cut into
the agar, creating precise measurements. For a more accessible way to cut the agar, it was best to
remove the agar from the deep dish it was provided in. This made for an easier way to cut the agar as
precisely as possible. The agar was removed using the back of the metric ruler, and then placed on a
sheet of paper towel.
Diffusion and Osmosis Lab Report pg.4
To prepare the solvent, 250 mL of HCl was poured into a 1000mL glass beaker. With a
stopwatch prepared, the three pieces of agar were simultaneously placed into the beaker. The acid
should cover the surface of the biggest piece,completely submerging the agar, and the timer began. A
watch glass was then placed to cover the top of the beaker. The agar was left submerged in the HCl for
12 minutes and 30 second.
When the time came to end, the watch glass was removed. The pieces of agar were removed
from the beaker, and moved onto a paper towel. The agar was removed by hand. As a safety
precaution, any skin that came in contact with the acid was thoroughly washed out to prevent chemical
burns. The three agar pieces were precisely sliced in half, exposing the boundary between the pink
square and the surrounding colorless section. A sharp box cutter was used to precisely cut the agar.
Permission and supervision from the lab instructor had to be provided.
Half of each agar size was then flipped on it’s side, so that the inner side was faced up. The
distance from the the purple square to the outside border of the colorless square was measured using a
metric ruler. This data was recorded. Once this information had been obtained, the agar was disposed
of.
Procedure 2: Modeling Diffusion and Osmosis
Materials:
(4) 200 mL beakers
(25 mL) 1.0 M NaCl solution
(3) Dialysis tubings
(2) 1 mL pipets
Tap water
Paper towels
Permanent marker
Stopwatch
Electronic balance
Masking tape
The procedure began with 4 cleaned 200mL beakers. Three of the beakers were then filled
with 200mL of water. These beakers were then labeled using masking tape and a permanent marker.
One beaker was labeled, “5mL,” another was labeled, “8mL,” and the third beaker was labeled
“12mL.” The fourth beaker was filled with 150 mL of tap water. The water in this beaker was used to
clean each pipet by filling the pipet with tap water from this beaker, and then rinsing out the inside of the
pipets.
Next, the bottoms of the three dialysis tubes were knoted. They were then each opened using
water to help expand the opening. Using one of the pipettes provided, one of the dialysis tubes was
filled with 5 mL of NaCl Solution. It was written down that this tube contained 5 mL of NaCl solution.
This tube was then put aside with the top end still open and untied.
Using the same pipet used previously, the second dialysis tube was filled with 8 mL of Nacl
solution and then marked down. Again, the third dialysis tube was filled with 12 mL of NaCl solution.
Using the electronic balance, this tube was weighed, and results were recorded.
Diffusion and Osmosis Lab Report pg.6
The top of the 12 mL dialysis tube was then tied and placed next to the beaker labeled “12 mL.”
Using the second pipet and the fourth beaker of water, the dialysis tube containing 5 mL of Nacl
solution was filled with 8 mL of tap water. Using the electronic balance, the tube was then weighed, and
results were recorded. The top of the dialysis tube was then tied and placed again next to, but not into,
the beaker labeled “5 mL.”
Using the same second pipet and the fourth beaker of water, the dialysis tube containing 8 mL
of NaCl solution was filled with 5 mL of tap water. Using the electronic balance, the tube was then
weighed, and results were recorded. The top of the dialysis tubing was tied and placed next to the
beaker labeled “8 mL.”
Each dialysis tube was then placed in its respective beaker. The tubing was completely
submerged in the tap water, and then left in the beakers for 10 minutes. A stopwatch was used to keep
track of the time. While the tubes were being submerged, pieces of paper towel were being prepared
onto the electronic balance to keep the tubes dry during their weigh­in to avoid weighing errors.
After 10 minutes, the tubes were removed from their beakers, carefully keeping track of what
tube contains what concentration of NaCl. The 5 mL NaCl solution tube was dried and placed on the
balance, and results were recorded. After rezeroing the balance, this was repeated for the 8 mL NaCl
solution tube and the 12 mL NaCl solution tube.
Procedure 3: Observing Osmosis in Living Cells
Materials:
Potato
Beakers
Cork Borer
Metric Rulers
Electric Balance
Color Coded Solutions
To begin, 200 mL of each sucrose solution was poured into four separate beakers. Extra
precaution not to mix these beakers with the beakers of other groups took place. These beakers were
put aside to begin coring the potato. A cork borer was used to cut out potato cores. Four potato cores
were created for the four sucrose solutions. Each core was trimmed to be approximately the same size.
Each core was then separately weighed using the electronic balance.
Each potato core was placed into a beaker with sucrose solution simultaneously, and a
stopwatch was used to keep track of the time. The potatoes soaked for 24 hours. Once they had
soaked for a full 24 hours, the potato cores were removed from their sucrose solution. Each potato
core was placed on a paper towel in front of its corresponding beaker as to not mix up the results. The
potato cores were then dried and weighed separately using an electric balance, and results were
recorded.
RESULTS
Procedure 1: Surface Area and Cell Size
The data from this procedure demonstrates the effect of HCl on Agar. These two graphs show the
effect the HCl had on the Surface Area of the Agar, as well as the effect it had on its volume.
Figure 1.1 shows the change in surface area after being removed from the HCl after 12 minutes and 30
seconds. Agar piece one began with a S.A. of 64 cm^2, and ended with a S.A. of 52.54. Agar piece
two began with a S.A. of 42 cm^2, and was removed to find that it had a S.A. of 27.5 cm^2. The final,
and smallest, agar piece had an initial S.A. of 24 cm ^2 and had a final S.A. of 10.14 cm^2.
Figure 1.2 shows the change in volume of the agar after removing it from the HCl after 12 minutes and
30 seconds. Agar piece one began with a volume of 32 cm^3, and was removed to find that it had a
volume of 23.4 cm^3. Agar piece two initially had a volume of 18 cm^3, and changed to a volume of
9.4 cm^3. The final piece of agar initially had a volume of 8 cm^3 and ended with a volume of 2.2cm^3
Figure1.1
Figure 1.2
Procedure 2: Modeling Diffusion and Osmosis
The results of this procedure show the weight difference of the dialysis tubes before and after
they were placed in the NaCl solutions.
Figure 2.1 is a table showing the weight difference of the dialysis tubes. The dialysis tube that
was placed in the 5 mL NaCl solution initially weighed 14.5g, and weighed 14.9g after the 10 minutes.
The dialysis tube that was placed in the 8 mL NaCl initially weighed 19g, and ended with a weight of
20.2g. The final dialysis tube that had been placed in the 12 mL NaCl solution had an initial weight of
20.1g and a final weight of 21.7g.
Figure 2.2 shows the percent change in the weight of the dialysis tubes. Dialysis tube one in the
5 mL NaCl solution had a weight gain of 2.76%. The 8 mL tube gained 6.32%. The dialysis tube in the
12 mL NaCl solution had a weight gain of 7.96%.
Figure 2.1
Amount of NaCL
solution
Weight before in
beaker (g)
Weight after in
beaker (g)
% change in weight
5 mL (0.417M)
14.5
14.9
2.76%
8 mL (0.667M)
19.0
20.2
6.32%
12 mL (1.0M)
20.1
21.7
7.96%
Figure 2.2
Procedure 3: Observing Osmosis in Living Cells
The data from Procedure 3 show the weight change of potato cores once placed in sucrose
solutions with different molar concentrations.
The Green solution caused a weight gain of 12.12% on the potato. The Blue solution caused a
weight gain of 3.03%. The Yellow solution caused a weight loss of 11.43%. The Pink solution also
caused a weight loss of 12.12%.
Color of Sucrose
Solution
Initial weight of
the potato cube (g)
Final weight of the
potato cube (g)
% change in weight
of the potato cube
(g)
Green
3.3g
3.7g
12.12%
Blue
3.3g
3.4g
3.03%
Yellow
3.5g
3.1g
-11.43%
Pink
3.3g
2.9g
-12.12%
Calculations based on weight change of potato cores
Color of Sucrose
Solution
Molar
Concentration
(prediction)
Solute Potential of
Water (bars)
Water Potential of
Potato (bars)
Green
0.2 M
­4.89
­4.89
Blue
0.4 M
­9.77
­9.77
Yellow
0.6 M
­14.66
­14.66
Pink
0.8 M
­19.55
­19.55
ANALYSIS/DISCUSSION
Procedure 1: Surface and Cell Size
The agar that had been provided by the teacher was cut into 3 individual cubes. These three cubes
would be part of a procedure to test the rate of diffusion on different size of cells. The three cubes of
agar were cut to 3 different sizes. After soaking the agar in HCl, Hydrochloric acid, for 12 minutes and
30 seconds, the results that were obtained were quiet obvious. It had been clear that the smallest agar
cube diffused the fastest. Agar piece one began with a S.A. of 64 cm^2, and ended with a S.A. of
52.54. Agar piece two began with a S.A. of 42 cm^2, and was removed to find that it had a S.A. of
27.5 cm^2. The final, and smallest, agar piece had an initial S.A. of 24 cm ^2 and had a final S.A. of
10.14 cm^2. In regards to volume, Agar piece one began with a volume of 32 cm^3, and was removed
to find that it had a volume of 23.4 cm^3. Agar piece two initially had a volume of 18 cm^3, and
changed to a volume of 9.4 cm^3. The final piece of agar initially had a volume of 8 cm^3 and ended
with a volume of 2.2cm^3. It was determined the size of the agar played a role in how much surface
area and volume was lost. The smaller the agar, the more surface area and volume it lost. In addition,
the acidity of the solvent affected the final size of each cube of agar.
Procedure 2: Modeling Diffusion and Osmosis
In this procedure, the predictions made in regards to the relationship of surface area and volume
in the artificial cells to diffusion rates. The dialysis tubing used represented models of living cells. This
included using 3 dialysis tubes in three different NaCl solution concentrations. After letting sit for 10
minutes, and after measurements had been completed, it was concluded that the cells filled with more
NaCl gained the most weight. The model cells with less glucose gained less weight. The dialysis tube
that was placed in the 5 mL NaCl solution initially weighed 14.5g, and weighed 14.9g after the 10
minutes. The dialysis tube that was placed in the 8 mL NaCl initially weighed 19g, and ended with a
weight of 20.2g. The final dialysis tube that had been placed in the 12 mL NaCl solution had an initial
weight of 20.1g and a final weight of 21.7g. Dialysis tube one in the 5 mL NaCl solution had a weight
gain of 2.76%. The 8 mL tube gained 6.32%. The dialysis tube in the 12 mL NaCl solution had a
weight gain of 7.96%. Based on the data composed in procedure 2, it was found that the amount of
NaCl present affected how much mass the dialysis tubes gained. A proportional relationship was found;
the more NaCl present, the more mass the dialysis tubes gained.
Procedure 3: Observing Osmosis in Living Cells
Four potato cores, all derived from the same potato, were placed into four different sucrose
solutions with different concentrations of sucrose. It was concluded that the higher the molar
concentration of the solution, the more weight the potato loses, because they are giving off water due to
the hypotonic solution they are in. The Green solution caused a weight gain of 12.12% on the potato.
The Blue solution caused a weight gain of 3.03%. The Yellow solution caused a weight loss of 11.43%.
The Pink solution also caused a weight loss of 12.12%.
CONCLUSIONS:
It can be concluded from procedure 1 that acid based solutions are efficient in breaking down
and diffusing substances like agar. Errors that could have come up while working on this procedure
would be errors in measurements. Measuring the size of the agar cubes was necessary when calculating
further data.
It can be concluded from procedure 2 that solutions with a high concentrations of NaCl are
directly linked to weight gain. Errors that could have come up when working on this procedure would
be mixing the dialysis tubes. Since the tubes were not labeled, this can very easily call for an error when
moving the dialysis tubes around and measuring them.
It can be concluded from procedure 3 that the masses of the potato cores were correlated to
whether they were in a hypertonic, hypotonic, or isotonic solution. Errors that could have arisen were
using different types of potatoes, or mixing the potatoes when removing them from the beakers, and
moving them to the electronic balance.
QUESTIONS:
1) If the agar had been placed in a more basic solution, how much volume and surface area would it
have lost?
2) What effect would wrapping the potatoes in procedure 3 have on the results? Would the process of
osmosis have been severely limited?
3) Would the length of the potatoes make it take longer for water to enter and exit the cells? What
about the width?
REFERENCES:
College Board (2013). Cellular Processes: Energy and Communication. Retrieved from
http://apcentral.collegeboard.com/apc/members/courses/teachers_corner/218954.html