The document summarizes experiments from a cell membrane transport lab that tested the rates of diffusion under different conditions. The first experiment tested osmosis and found that a dialysis cell immersed in a solution gained mass over one hour due to water diffusion. Subsequent experiments tested diffusion rates in a gel, liquid, gas, and through filtration. The gel experiment found temperature affected diffusion rates, while liquid and gas experiments supported diffusion being inversely related to temperature. The filtration experiment showed larger particles were filtered out over time. Overall, the experiments supported theories of diffusion and osmosis being impacted by various environmental factors.

1. Cell Membrane Transport
Aubrien Henderson
ZOOL 2011.02
Angela Agogo
February 23, 2015
Introduction

2. The Cell Membrane Transport Lab (CMT) conducted experimentation that overall tested
the rates of diffusion when placed under various conditions or encountered different variables.
Cell membrane transport is based on the concept of diffusion. Diffusion is the random movement
of molecules from an area of higher concentration to an area of lower concentration through a
semi-permeable membrane. According to the theory of diffusion, molecules move in and out of
cells depending on the concentration of solution or substance and the permeability of that cell. A
semi-permeable membrane is a cell membrane that allows specific molecules pass in and out
while blocking others. The process of diffusion can be applied to many different areas of study,
including in relation to the human body. This can be seen by the work conducted by researchers
that use Diffusion Weighted Magnetic Resonance Imaging to determine the “diffusivity of water
molecules in the human body” (Kwee, 409-417). In relation to the human body, researchers are
conducting studies that analyze the diffusion of antibodies, proteins, and other molecules through
mucosal membranes that cover cells and are thought to act as a “diffusional barrier” which
protects epithelial cells (Saltzman, 508-515).
The concept and practice of cellular membrane transport is vital to the survival of the
cells. The ability to move substances into the cell via membrane transport allows for the cell to
take in necessary particles to sustain its metabolic reactions and also to rid its interior of the
cellular waste products resulting from cell exportation (Tortora, 64). Having selective
permeability in the cell’s plasma membrane allows the process of simple diffusion to take in and
carry out oxygen, carbon dioxide, and most soluble lipids (yvcc.edu). Passive processes of
cellular transport, i.e. diffusion, allows for the cell’s internal environment and external
environment be at equilibrium (where the concentration of solution outside the cell equals that
inside the cell). Diffusion and other cellular membrane transports enable the

3. cell to adjust to hypotonic and hypertonic environments, preventing hemolysis (swelling of the
cell) and crenation (shrinking of the cell) when exposed to hypotonic and hypertonic solutions.
This lab studied the effects of various environmental changes on the rate of cellular membrane
transport, specifically through diffusion and osmosis. This lab was separated into five different
experiments which consisted of experimentation on the process of osmosis, diffusion in a gel,
diffusion in a liquid, diffusion through the air, and filtration (CMT, 1).
The first experiment performed in this lab tested and observed the process of osmosis.
Osmosis is a passive transport process in which water will move into whichever environment
(interior or exterior) has a greater concentration of molecules (higher tonicity). Reverse osmosis,
prevalent in medical and environmental fields, paired with nanofiltration and ultrafiltration, are
used specifically in studies that aim to separate pharmaceuticals from water bodies to decrease
the pollution of these chemicals in the water consumed by people (Dolar, 319-344). This
experiment looked at the process of osmosis through two tests, “Osmosis” and “Biochemical
Testing” (CMT, 2-3). In the experiment labeled “Osmosis”, the process of osmosis was tested by
weighing the mass of a “dialysis cell” before the experiment and an hour after being immersed in
the “environment” (deionized water). The dialysis cell was filled with cytoplasm and the dialysis
tubing acted as the semi-permeable membrane. It was hypothesized that if osmosis is directly
related to the tonicity of a solute, then the dialysis cell immersed in the environment would gain
more mass in the form of water molecules at the end of a one hour time period.
In the experiment labeled “Biochemical Testing”, the same environment and cytoplasm
used in the “osmosis” section were used for the testing of positive presence of sugar, protein,
chlorine ions, and starch. This was observed through four different tests: Glucose, Albumin,
NaCl, and Starch. Each of the four tests contained two test tubes: an environment test tube and a

4. cell test tube which contained the cytoplasm. In the Glucose test, Benedict’s solution was used to
test for the presence of sugar. In the Albumin test, a Biuret solution was used to test for protein.
In the NaCl test, silver nitrate (AgNO3) was used to test for chlorine ions. In the last of the four
tests, the Starch test, Lugol’s iodide was added to test for starch. These four tests that are labeled
under the Biochemical Testing are a part of the same overall experiment that tests osmosis and
observes its characteristics, thus the Biochemical Testing and the Osmosis will be classified as a
singular experiment.
The second experiment conducted observed the rate of diffusion in a semi-solid
substance. Diffusion can occur at different rates depending on such factors as temperature,
surface area, etc. One of these factors is the type of substance the solute is placed in- its state of
matter, whether it be liquid, solid (gel), or gas. To test the rate of diffusion, on two agar plates
were distributed two drops of methylene blue and two drops of a potassium permanganate
solution each. One plate was kept at room temperature while the other was labeled the “cold
plate” and was kept on ice. The diameter of the drops in each plate was recorded in ten minute
intervals over the span of one hour. It was hypothesized that if the methylene blue drops and the
potassium permanganate drops were kept in the ice bath, then they would show an overall
decrease in size compared to those left at room temperature.
The third experiment in the lab tested the rate of diffusion in a liquid solution. As stated
above, the rate of diffusion can vary depending on the state of the substance used as the solution
and the temperature. This experiment specifically observed and compared the rate of diffusion in
a flask filled with deionized water kept at room temperature and another in an ice bath. One mL
of blue dye was dropped in each flask and, without aid in the diffusion process through swirling,
shaking, or stirring the flask, the time for the blue dye to completely permeate the water solution

5. was recorded. It was hypothesized that if the rate of diffusion was inversely proportional to
temperature, then the rate of diffusion will decrease as the liquid became colder.
The fourth experiment conducted tested the rate of diffusion in gas particles. This
experiment had the instructor spray a gas (lysol air freshener) from a designated release site. As
the gas particles diffused through the air, students recorded the time it took to reach their
designated distance/position. It was hypothesized that if the rate of diffusion of the gas particles
decreased as the distance that it has to spread through increased, then the rate of diffusion for the
first few groups would be higher than that of the last few groups.
The fifth and final experiment of the lab tested how particle size and solubility affect the
process of filtration. Filtration is an important characteristic of the plasma membrane of a cell as
it allows it to have the quality of selective permeability, by which it allows particles of a certain
size pass through while preventing larger particles from entering the cell. Filtration is seen in the
human body by the kidneys and their ability to filter out toxins from entering the bloodstream.
Kidneys are so crucial to the health of a person that people whose kidneys do not function
properly must have medical treatment in the form of dialysis or kidney transplant (Gozdowska,
2592-2597). Filtration is also used in the Medical field for the creation of large concentrations of
active viruses that are taken from human hosts and later used to make vaccines (Charcosset, 143-
167). To test the process of filtration, a mixture of Copper Sulfate crystals, deionized water, and
charcoal was created and poured into an Erlenmeyer flask after passing through funnel
containing a coffee filter. Once the mixture began passing through at a countable pace, the
number of drops entering the flask were counted in fifteen second intervals over the span of
ninety seconds. It was hypothesized that if filtration is affected by the particle sizes in the
mixture being filtered, then the largest particles (the charcoal) would be caught by the filter while

6. the smaller particles and the particles that have been dissolved (the distilled water and copper
sulfate) would seep through the filter.
Methods and Materials
(TWU 2015)
Results
Table 1. Osmosis - Dialysis Cell
Time
(Hours)
Mass
(Grams)
0 19.5
1 20
Table 1 shows the mass of the dialysis cell at the beginning of 1 hour and then at the end of the 1
hour after being immersed in the environment solution.
Table 2. Osmosis - Biochemical Testing
Tests Cell Environment
Glucose (Sugar) + +
Albumin (Protein) + +
NaCl (Chlorine ions) + +
Starch (Starch) + -
Table 2 shows whether the cell and environment test tube solutions tested positive or negative
for the presence of sugar, protein, chlorine ions, and starch.
The two tables shown above give the data for the first experiment, “Osmosis”. Table 1
shows that the dialysis cell (dialysis membrane filled with cytoplasm) after being fully immersed
in the environment solution for 1 hour increased in mass by .5 grams, beginning at 19.5 grams at
the start of 1 hour and ending at 20 grams at the end of 1 hour. Table 2 shows the solutions that
tested positive or negative for sugar, protein, chlorine ions, and starch. The cell test tube tested
positive for all of the above conditions while the environment test tube tested positive for sugar,
protein, and chlorine ions, and negative for the presence of starch.
Graphs 1-4. Diffusion in a Gel

7. Graph 1. Methylene Blue at Room Temperature
Graph 1 shows the diameter (in millimeters) of the two methylene blue gel drops tested at room
temperature. The diameter measurements were taken in 10 minute intervals over the span of 60
minutes.
Graph 2. Potassium Permanganate at Room Temperature
Graph 2 shows the diameter of the two drops of potassium permanganate (in millimeters) tested
at room temperature. The diameters were measured in 10 minute intervals for a span of 60
minutes.
Graph 3. Methylene Blue in Ice Bath
Graph 3 shows the diameter of the two drops of methylene blue (in millimeters) kept in an ice
bath. The measurements of diameter were taken in 10 minute intervals for a span of 60 minutes.

8. Graph 4. Potassium Permanganate in Ice Bath
Graph 4 shows the diameter of the two drops of potassium permanganate (in millimeters) kept in
an ice bath. The diameters were measured in 10 minute intervals for a span of 60 minutes.
The Graphs above represent the data collected for the second experiment of the lab,
Diffusion in a Gel. The methylene blue drops kept at room temperature (Graph 1) fluctuate in
diameter for the first 40 minutes of the study, but then remain constant for the last 20 minutes.
Although they fluctuated for the first 40 minutes, they did not show a net increase or decrease in
diameter. The potassium permanganate drops kept at room temperature (Graph 2) fluctuate in
diameter for the first 30 minutes of the study showing no significant net increase or decrease in
diameter. However, for the next 20 minutes, the diameters of both drops steadily increase in
diameter at the same rate, while plateauing for the last 10 minutes. The two drops of methylene
blue kept in the ice bath (Graph 3) show a decrease in diameter for the first 10 minutes, a slow
increase for the next 20 minutes, and plateau for the last 30 minutes of the steady. The last graph
(Graph 4) shows the two drops of potassium permanganate kept in an ice bath. These drops show
a steady rate of increase in diameter for the first 50 minutes of the study, and plateau for the last
10 minutes.
Table 3. Diffusion in a Liquid
Time
(Minutes)
Rate of Diffusion
(mL/hr)

9. Flask #1 39 155.38
Flask #2 8 776.92
Table 3 shows the time (in Minutes) and rate of diffusion that it took for the blue dye to
completely diffuse in the distilled water without aid from an experimenter. Flask #1 represents
the flask that was placed in the ice bath and Flask #2 represents the flask that was kept at room
temperature.
Table 3 refers to the third experiment in the lab, Diffusion in a Liquid. Two flasks were
filled with deionized water and 1mL of blue dye dropped into each flask. Flask #1 was kept on
ice to remain at a cold temperature and took 39 minutes for the dye to fully diffuse in the water
without the aid of the experimenter. Flask #2 was kept at room temperature and took 8 minutes
for the dye to fully diffuse in the water.
Table 4. Diffusion in Air
Group Distance
(Meters)
Time
(Seconds)
Diffusion Rate
(Meters/Seconds
)
Average Rate of
Diffusion (m/s)
1 3.84 33 0.12 0.10
2 6.43 54 0.12 0.10
3 9.14 99 0.09 0.10
4 11 101 0.11 0.10
5 6.76 79 0.09 0.10
6 6.2 69 0.09 0.10
Table 4 shows the rate of diffusion of the aerosol particles starting from the release site. Each
group represents a different distance in the room and calculated the distance they were at, the
time it took for the gas particles to reach them, the diffusion rate, and the average diffusion rate.
The table refers to the fourth experiment of the lab, Diffusion in the Air. Gas particles in
the form of an aerosol scent (lysol air freshener) were sprayed into the room by the instructor at a
designated release site. Each of the six groups recorded the time and the distance it took for the
particles to reach the designated spot at their table and from that data, the rate of diffusion and

10. the average rate of diffusion for the class was calculated in meters/seconds. The average rate of
diffusion for the class was 0.10 m/s.
Table 5. Filtration
Time
(Seconds)
Number of
Drops
15 18
30 5
45 2
60 1
90 0
Table 5 shows the number of drops of the liquid (a mixture of deionized water, copper sulfate,
and charcoal) which passed through the filter. The number of drops are recorded over the span of
90 seconds in 15 second increments.
The table above refers to the fifth and final experiment of the lab, Filtration. Once the the
solution poured through the filter slowed to a countable pace, the number of drops of the solution
were counted in intervals of 15 seconds for 90 seconds total. As the time passed increased, the
number of drops of solution decreased to eventually stop and have 0 drops for the last interval of
time. Overall there was a total of 26 drops that went through the filter at a countable pace over
the span of 90 seconds.
Discussion
The first experiment, Osmosis, recorded in data Table 1, showed an overall increase in
mass of the dialysis cell. According to the theory of osmosis, this increase in mass can be
attributed to a greater concentration of water molecules in the environment solution than in the
dialysis cell. The dialysis gained mass through the acquirement of water molecules that entered
through the semi-permeable membrane. The gained mass can be identified as water molecules
and not foreign substances because the process of osmosis itself is a specific type of diffusion

11. that deals with molecules of water. The results of this experiment supported the hypothesis given
as it predicted the dialysis cell would gain mass by the end of the 1 hour time frame. The second
portion of this experiment testing osmosis was recorded in Table 2. The test tube filled with the
cell solution approved what was stated in the lab Methods and Materials that stated the cell
should test positive for all substances- sugar, protein, chlorine ions, and starch (CMT, 3). The
environment solution filled test tube, which was deionized water, tested positive for sugar,
protein, and chlorine ions, however tested negative for starch.
In the second experiment conducted, Diffusion in a Gel, Graphs 1-4 showed the net
increase or decrease in diameter of the gel as time passed. The drops of methylene blue at both
room temperature and in the ice bath showed little net change in diameter. The diameter size of
the methylene blue drops at room temperature plateaued in diameter at 1 mm while the
methylene blue drops in the ice bath plateaued at 0.8 mm. A possible cause for this decrease in
size accompanied by the change in temperature is that as molecules are placed in a colder
temperature, they condense and often become a denser, smaller version of the substance. The
diameter size of the potassium permanganate drops at both room temperature and ice bath
conditions showed a slow rate of increase. The potassium permanganate drops at room
temperature plateaued with a diameter size of 1.8 mm while the potassium permanganate drops
in the ice bath plateaued at a slightly smaller size of 1.7 mm. These results are consistent with the
causes listed above for the methylene blue drops. Overall, the data from this experiment
approves the hypothesis as both types of drops in the ice bath saw an overall decrease in size
compared to the drops kept at room temperature.
The third experiment conducted in the lab, Diffusion in a Liquid, was recorded in
Table 3 of the Results. The rate of diffusion of the blue dye in the deionized water was

12. significantly lower for the flask kept on ice taking 39 minutes than the flask kept at room
temperature which took 8 minutes to completely diffuse. This was caused by different rates of
kinetic energy of the molecules making up the solution. Kinetic energy is the movement of
particles within the solution it forms. The greater the kinetic energy was, the faster the particles
will move around within the solution and the faster the rate of diffusion would be. When a
solution was placed under the condition of a colder temperature, the kinetic energy decreased as
the particles within the solution moved more slowly. The hypothesis stated for this experiment in
the introduction can be accepted because of this data, as the hypothesis predicted a slower rate of
diffusion for the flask kept in the ice bath than that of the flask kept at room temperature.
In the fourth experiment, Diffusion in the Air, represented by Table 4 the average rate of
diffusion was calculated by recording each of the six groups data. Based on the concept of
kinetic energy mentioned above and its relevance to the rate of diffusion of that solution or
substance, it can be predicted that the rate of diffusion will be the greatest in gas particles (the
air) and slowest in solids or semi-solids (gel), with liquids falling somewhere in between these
two states of matter. This experiment showed a relatively stable rate of diffusion, however did
have a slight decrease in diffusion rate for Groups 5 and 6. This supported the hypothesis given
because Groups 5 and 6 were farther from the release site, and would attribute this decrease in
diffusion rate to the increased amount of distance that the gas particles were required to cover.
This showed that the rate of diffusion is inversely proportional to the distance or size of the room
that is undergoing the process of diffusion. This experiment has potential limitations in its data
because the data was collected from six separate groups and are not uniform in their practice of
observing the particles (smelling the aerosol)l, measuring the distance from the release site to
their designated position, or keeping time.

13. The fifth experiment of the lab, Filtration, was addressed in Table 5 of the Results. The
overall rate of filtration decreased as the time passed increased. This makes sense because as the
solution was poured into the Erlenmeyer flask, the filter was used to stop larger particles from
going through. By the end of the 90 second time period, the filter had separated a majority of the
charcoal from the rest of the mixture. Using a better filter would allow for the trapping of more
charcoal particles. The data from this experiment supported the hypothesis given because it
showed a decrease in number of drops of the mixture filtered through over the time period of 90
seconds and the filter kept the largest particles (charcoal) from passing through it.
Conclusion
As mentioned in the Introduction, the purpose of this lab was to observe and test the rates
of diffusion when exposed to different conditions, such as temperature and state of matter. It also
analyzed the processes of osmosis and filtration. These processes are essential to the life of a cell
and therefore essential to the life of people and animals, and studying them allowed for a better
understanding of how to prevent the disturbance of such processes. In future studies,
experimenters could conduct the experiments over longer periods of time and in greater
quantities to find a greater correlation between such factors as temperature, kinetic energy, and
size of solution in relation to diffusion. They could also expand the study to include other types
of cell membrane transports, such as active transport.
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tm