Name___________________________
Mrs. Geithner-Marron (Bio 300)
"Dialysis Tubing Cell” Lab (Osmosis & Diffusion)
Date _________
Period ________
Background: It is very difficult to measure or see osmosis and diffusion actually occurring in cells
because of the small size of most cells. However, if an artificial membrane that acts in some ways
like a real plasma (cell) membrane could be found, than a study of osmosis and diffusion using a
model cell would be possible.
Dialysis tubing is a manmade semi-permeable membrane that is used to treat people who have
kidney failure. Dialysis is a process where substances in solution are separated by their
differences in molecular weight (size). The driving force behind dialysis is the concentration
gradient (or difference) between two solutions on opposite sides of the membrane.
In this lab, we are going to make model “cells” and place different materials inside and outside of
the cell. This will allow us to see which materials can/cannot pass through the “cell” membrane.

To test for starch, we will use iodine as an indicator.
o When starch is present, iodine will turn from orange-brown to

.
To test for glucose, we will use a “glucose test strip” as an indicator.
o When glucose is present, the colored end of the test strip will change color (according to
the directions on the package) from
to
.
(This diagram is similar to
how we will set up our lab.)
________________________________________________________________________________
Materials: (per lab team)

(1) 250 mL beaker

(1) 12 cm length of dialysis tubing
o
soaked in warm water overnight

1 mL supersaturated glucose solution with pipette
o
15 g glucose/100 mL water

iodine solution

(2) pieces of cotton string ~10 cm long

tap water

5 ml starch solution with pipette

(3) glucose test strip(s)

electronic balance
o
5g starch/100 mL of water
Name___________________________
Mrs. Geithner-Marron (Bio 300)
"Dialysis Tubing Cell” Lab (Osmosis & Diffusion)
Date _________
Period ________
Procedure:
1. Gather a 250 ml beaker and label it with your group members’ names and period #.
2. Then, add 150 ml of tap water to the beaker (and put it off to the side, where nothing can
get in it.)
3. Gather 1 piece of pre-soaked dialysis tubing and 2 pieces of string.
4. Under gently running water, rub the tubing between your fingers
Open
tubing
under
running
water.
until it opens up.
a. BE GENTLE!!! DIALYSIS TUBING IS EASILY TORN!!!
5. Then, (~ 1-2 cm from the end) fold over the tubing, twist it, and
tie the string around it (as tight as possible).
a. You may want to wrap the string around the "tail" again and tie it a
fold,
twist, &
tie
second time.
6. Carefully, fill the tube with water (without tying the other end) and
check for any leaks.
a. If no leaks are found empty the tube & go to step 7.
b. If leaks are found, tie the string around the "tail" again and retest for leaks.
7. Using a pipette, add the glucose solution to the tube until the tube
is ~1/3 full.
8. Using a second pipette, add the starch solution to the tube until
the tube is ~2/3 full.
fold, twist,
and tie
9. A little above the top of the starch and glucose solution, fold and
twist the top end of the tube closed and tie the string around it.) You have now made a “cell”!)
Name___________________________
Mrs. Geithner-Marron (Bio 300)
"Dialysis Tubing Cell” Lab (Osmosis & Diffusion)
Date _________
Period ________
10. Cut off any excess string from both ends.
11. Rinse the "cell" off under gently running water in order to make sure there is no starch or
glucose solution on the outside (which could alter your results) and place it on a paper towel.
12. Test the water in the beaker for the presence of glucose (using a test strip). NOTE: It may
take a few minutes to see results.
13. Add a few drops of iodine to the water in the beaker so the water turns yellow/golden-orange.
14. Record information for the location of all four substances (glucose, starch, iodine, and
water in the "Initial observations: Where did it start?" column on data table.
15. Record your predictions (or what you think will happen to each substance in the "Predict:
Where do you think it will end up?" column on your data table.
16. Find the mass of the "cell". __________________________
17. Place the "cell" in the beaker of water, and add water if necessary to cover the tube.
18. Leave the beaker on the counter in the designated area.
19. Clean up your lab area and return materials to the designated area.
Name___________________________
Mrs. Geithner-Marron (Bio 300)
"Dialysis Tubing Cell” Lab (Osmosis & Diffusion)
Date _________
Period ________
20. On, the attached blank diagram sheet, diagram your
initial set-up (similar to the picture on the right)
showing what it looked like at the very beginning of
glucose
the experiment (once you put the "cell" in the water).
water + iodine
a. Use different colors and/or symbols to represent
the different molecules (starch, glucose, iodine, water).
b. Make sure to label all parts/make a key.
21. On, the attached blank diagram sheet, diagram your
set up showing your predictions (based on what you
glucose
circled in the "Predict: Where do you think it will
end up?" column of you data table).
water + iodine
a. Use arrows to represent your predicted movements for each substance.
b. Use the same colors, symbols, & key as you did in your "before" diagram.
22. After waiting for a given amount of time, observe your "cell" to see what changes have taken place.
a. Test the water in the beaker for the presence of glucose (using a test strip). NOTE: It
may take a few minutes to see results.
i. Record results in the "Final observations: Where did it actually end up?"
column of the data table.
b. Record results for other substances (starch, iodine, glucose, & water) "Final observations:
Where did it actually end up?" column of the data table. (For glucose you will test the
water in the beaker and cut the "cell" open to test the
water inside the "cell".
23. On, the attached blank diagram sheet, diagram your final
glucose
set-up (similar to the picture on the right) showing what it
looked like at the very end of the experiment.
water + iodine
a. Use the same colors, symbols, & key as you did in your "before" and "predictions" diagrams.
Name___________________________
Mrs. Geithner-Marron (Bio 300)
"Dialysis Tubing Cell” Lab (Osmosis & Diffusion)
Date _________
Period ________
Data and Observations:
Location of Molecules of Glucose, Starch, Iodine, and Water in Model "Cell" and Beaker Set-up
substance
Initial observations:
Predict:
Final observations:
Where did it start?
Where do you think it will
Where did it actually end
end up?
up?
(circle one for each substance)
(circle one for each substance)
(circle one for each substance)
glucose

in the beaker

in the beaker

in the beaker

in the "cell"

in the "cell"

in the "cell"

in both the beaker &

in both the beaker &

in both the beaker &
the cell
starch
the cell

in the beaker

in the beaker

in the beaker

in the "cell"

in the "cell"

in the "cell"

in both the beaker &

in both the beaker &

in both the beaker &
the cell
iodine
the cell
the cell

in the beaker

in the beaker

in the beaker

in the "cell"

in the "cell"

in the "cell"

in both the beaker &

in both the beaker &

in both the beaker &
the cell
water
the cell
the cell
the cell

in the beaker

in the beaker

in the beaker

in the "cell"

in the "cell"

in the "cell"

in both the beaker &

in both the beaker &

in both the beaker &
the cell
the cell
the cell
Name___________________________
Mrs. Geithner-Marron (Bio 300)
"Dialysis Tubing Cell” Lab (Osmosis & Diffusion)
Date _________
Period ________
Diagrams for Location of Molecules of Glucose, Starch, Iodine, and Water
in Model "Cell" and Beaker Set-up
Initial set-up

Observations: In the space below, list any other
observations or measurements you make BEFORE
and AFTER putting the "cell" in the beaker.
o
***Make sure you take detailed notes
because you may have a QUIZ on this lab!!!!

Before (observations & measurements when you
first set up your lab):
Predictions

After (observations & measurements at the end
of your lab):
Final set-up