3) OSMOSIS AND
DIALYSIS
Sucrose
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Experiment #3
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There are two parts to thisTo
experiment
3. PART 1
magnify#the
will consider OSMOSIS and
PART 2 will click
consider
blackboard
on it
DIALYSIS. You will need toto
supply
following in
view the
a discussion
your lab report for experiment # 3
on membrane
Part 1 (Osmosis)
transport
Table of Osmotic Potential and Time
Graph of Osmotic Potential vs Time
Graph of Osmotic Change vs Time (Osmotic
Rate)
Answers to Questions (1 - 7)
Part 2 (Dialysis)
Table of Dialysis Tests
Answers to Questions (1 - 6)
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OSMOSIS is the diffusion of water through a
selectively permeable membrane. Water will
generally move quite freely through the cell
membrane by diffusion. Osmotic movement
of water occurs when the solute (nonpenetrating) concentrations differ between
the opposing sides of the cell membrane. A
difference in solute (non-penetrating)
concentrations means there is a difference in
water concentrations and water will move
from the region of higher concentration to a
region of lower concentration.
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For example, water osmotically moves into a
cell when the fluid outside the cell has more
water (less solutes) than the fluid inside the
cell. In this case, as water moves into the
cell, it swells as the water pressure inside
the cell increases.
Red Blood Cell
Distilled Water
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DIALYSIS is the separation of solutes
according to their size by diffusion through a
permeable membrane. Depending upon the
molecular pore size of the membrane,
solutes will either diffuse across the
membrane or be restricted by their size.
The device you will be using to collect data
for the experiments is an osmometer. This is
a device used to measure osmotic force.
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PART 1 (OSMOSIS)
MATERIALS
Thistle tube (with mm markings)
Thistle tube stand
Dialysis tubing (selectively permeable
membrane)
Rubber band
Sugar solution (20 % sucrose)
Beaker
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When you are finished with PART 1 of
experiment # 3, be sure that you include the
following with your lab report.
Table of Osomotic Potential and Time
Graph of Osmotic Potential vs Time
Graph of Osmotic Change vs Time
(Osmotic Rate)
Answers to Questions (1 - 7)
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Sucrose
Sucrose
H2O
H2O
You will need to record your
data from this experiment on
a data table. You can access
the data table by clicking on
the link to the right.
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Instructions on the Blackboard
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Access the Data Table
STAND
Sucrose
Sucrose
H2O
H2O
Procedure
Click on the thistle tube stand in
order to bring it to the table
You will know you are pointing
to the stand when the cursor
changes.
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Instructions on the Blackboard
Sucrose
Sucrose
H2O
Thistle tube
H2O
Now click on the thistle tube
funnel to attach it to the tube
stand.
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Instructions on the Blackboard
Tubing
Sucrose
Sucrose
H2O
H2O
Next we will put the dialysis
tubing on the bulb end of the
thistle tube. You will need
only a small piece. Click on
the dialysis tubing on the
shelf.
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Instructions on the Blackboard
Sucrose
Sucrose
H2O
H2O
Rubber Band
Put a rubber band on the tube
and dialysis tubing to hold it
in place. You can accomplish
this by clicking on the rubber
bands on the shelf.
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Instructions on the Blackboard
Sucrose
Sucrose
H2O
H2O
Put the bulb of the thistle
tube into the beaker of water.
The water is distilled which
means that it has no solutes
in it (100 % water). Click on
the beaker labeled as H2O.
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Sucrose
Sucrose
Now we will pour the sucrose
solution into the thistle tube
from the top. The sucrose
solution is a 20 % sugar solution
(80 % water). Click on the beaker
labeled as Sucrose.
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Instructions on the Blackboard
33
30
26
22
16
Record the original millimeter
measurement of the sucrose
solution in the column of the thistle
tube on your data sheet. Next,
record the movement of the sucrose
solution every 15 minutes for 90
minutes. Click on the start button of
the clock to begin measuring.
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Instructions on the Blackboard
START
10
3
00:00
90:00
85:00
80:00
75:00
70:00
65:00
60:00
55:00
50:00
45:00
40:00
35:00
30:00
25:00
20:00
15:00
10:00
05:00
From the data you have
collected you will need to
produce two graphs. One of the
graphs will plot Osmotic
Potential vs Time. The other
graph will plot Osmotic Change
vs Time.
Graph of Osmotic
Potential vs Time
Graph of Osmotic
Change vs Time
You may want to print the two links
above to produce your graphs.
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Instructions on the Blackboard
When you have finished
your graphs you can
compare them with the two
links below. Yours should
be very similar to these.
Completed Graph
of Osmotic
Potential vs Time
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Instructions on the Blackboard
Completed Graph
of Osmotic
Change vs Time
Answer the following
questions about the
experiment you have
performed. Be sure to
include the answers in
your lab report.
Questions 1 - 7 on
Osmosis and Dialysis
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Instructions on the Blackboard
When you are finished with part 1 of
experiment # 3, be sure that you include the
following with your lab report.
Table of Osomotic Potential and Time
Graph of Osmotic Potential vs Time
Graph of Osmotic Change vs Time
(Osmotic Rate)
Answers to Questions (1 - 7)
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You are now ready to begin
part two of experiment #3.
Lugol’s
Lugol’s
Glucose
Glucose
H2O
Starch
H2O
Starch
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Instructions on the Blackboard
In this part we will be
concerned about a process
related to osmosis called
Dialysis.
Dialysis is the diffusion ofTo
a solute
(salt, the
glucose,
magnify
etc.) across a selectively permeable membrane. In
blackboard click on it
this case the solute molecules always move from
to(hypertonic)
view a discussion
the stronger concentration
to the
about dialysis
weaker (hypotonic).
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Instructions on the Blackboard
Dialysis involves the movement of some, but
not all, of the dissolved substances in a
solution. The substance that moves has small
molecules, so these can pass through the
pores in the membrane, but other substances,
with larger molecules, cannot escape.
The green molecules
are small enough to fit
through the pores of
the semi permeable
membrane while the
red molecules are too
large.
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This process occurs normally in the kidney.
Substances with small molecules, such as
salts, glucose and urea, continuously pass out
of the blood through a membrane under
pressure, but useful substances are later
reabsorbed. Waste substances are then
excreted as urine.
Kidney
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In this exercise you will measure diffusion of
small molecules through dialysis tubing, an
example of a semi permeable membrane.
The movement of a solute through a semi
permeable membrane is called dialysis. The
size of the minute pores in the dialysis
tubing determines which substance can
pass through the membrane.
The light blue object here
represents a section of dialysis
tubing. The red spheres represent
molecules which are able to move
through the dialysis membrane,
while the blue spheres represent
molecules too large to move out
of the dialysis membrane
solution.
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Instructions on the Blackboard
A solution of glucose and starch will be
placed inside a bag of dialysis tubing.
Distilled water will be placed in a beaker,
outside the dialysis bag. The dialysis bag
with the starch glucose solution will be
inserted into the beaker of distilled water.
After 30 minutes have passed, the solution
inside the dialysis tubing and the solution in
the beaker will be tested for glucose and
starch. The presence of glucose will be
tested with glucose test strips. The presence
of starch will be tested with Lugol's solution
(iodine potassium iodide).
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Instructions on the Blackboard
PART 2 (DIALYSIS)
MATERIALS
30 cm section of dialysis tubing
String
15 % glucose solution
1 % starch solution
Glucose test strips
Lugol’s solution
Distilled water
2 Test tubes
Large beaker
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Instructions on the Blackboard
When you are finished with Part 2 of
experiment # 3, be sure that you include the
following with your lab report.
Table of Dialysis Tests
Answers to Questions (1 - 6)
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Procedure
Obtain a 30 cm piece of dialysis
tubing
Lugol’s
Tubing
Lugol’s
Click on the tubing to obtain
the dialysis tubing
Glucose
Glucose
H2O
Starch
H2O
Starch
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Instructions on the Blackboard
We will now tie one end of
the dialysis tubing with
the string.
Lugol’s
Lugol’s
Click on the string to tie
the tubing
Glucose
Glucose
H2O
Starch
H2O
Starch
String
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Instructions on the Blackboard
We can now place the dialysis
tubing in distilled water to moisten
it so that it will be easier to open.
Lugol’s
Lugol’s
Glucose
Glucose
H2O
Starch
H2O
Starch
Click on the beaker of distilled
water to bring it to the table then
click on the dialysis tubing to place
the tubing in the water.
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Instructions on the Blackboard
While we let the dialysis tubing
soak, we can access the
glucose and starch solutions.
Lugol’s
Lugol’s
Bring the two solutions to the
table by clicking on either of
them.
Glucose
Glucose
Starch
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
We will need to develop a
method to test for glucose
in a solution as well as
test a solution for starch.
Lugol’s
Lugol’s
Glucose
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Use a table like the one you
see below to record your
results.
Lugol’s
Lugol’s
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Instructions on the Blackboard
Glucose
H2O
You can use the link supplied
below to view a table which
can be printed.
Starch
You should indicate a positive or negative test for each
of the solutions and tests in the spaces provided
Glucose Test
Tape
Lugol’s
Solution
Glucose Solution
Starch Solution
Dialysis Tube Solution After Soaking in
Starch
Glucose
Distilled
Water
Beaker of Distilled Water Before Insertion
of Dialysis Tube
Beaker of Distilled Water After Insertion of
Dialysis Tube
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Printable Version of
This Table
We will be using glucose test
strips to test a solution for the
presence of glucose.
Lugol’s
Lugol’s
When the strip is exposed to
glucose it will change color
from yellow to blue.
Glucose
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
We will be using Lugol’s
solution to test for the
presence of starch.
Lugol’s
Lugol’s
When Lugol’s solution is in the
presence of starch the solution
will change to a dark blue color.
Glucose
H2O
Water
Starch
Starch
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Instructions on the Blackboard
Click on the test strips to bring
them to the table.
Lugol’s
Lugol’s
Glucose
H2O
Glucose
Test Strips
Next we will test the Glucose
solution and the distilled water
where the dialysis tubing is now
soaking for the presence of
glucose.
Starch
Starch
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Instructions on the Blackboard
Click on one of the glucose test
strips.
You will be testing the glucose
solution for the presence of
glucose.
Lugol’s
Lugol’s
Glucose
H2O
As you have predicted, you will get
a positive test. Record your data.
Starch
The color change on the
strip shows a positive test
for the presence of glucose
Glucose
Starch
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Instructions on the Blackboard
Click on another test strip to test
the distilled water for the presence
of glucose.
Lugol’s
Lugol’s
Remember a positive test will turn
the yellow end of the strip to blue.
Glucose
H2O
Record your results in your data
table.
Starch
Record your data
Glucose
Starch
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Instructions on the Blackboard
Next we will test for starch in the
starch solution and the distilled
water.
Lugol’s
You will be using Lugol’s solution
to test for starch.
Lugol’s
Glucose
H2O
Glucose
If starch is present the solution will
turn a dark blue color.
Starch
Starch
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Instructions on the Blackboard
Click on the blue bottle of Lugol’s
solution on the shelf to bring it to
the table.
Lugol’s
Lugol’s
Test tube
You will need a test tube to test a
small portion of the starch
solution.
Glucose
Next click on the test tube rack.
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Next
theofeyedropper
in
Clickclick
on on
one
the
the
bottle of Lugol’s
solution
eyedroppers
on the
shelfto
add a few drops to the starch
to add starch to the test
solution in the test tube.
Lugol’s
tube.
Record your results on your
data sheet.
Glucose
Eye Dropper
Glucose
H2O
Starch
Starch
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Instructions on the Blackboard
Next we will test the
distilled water for the
presence of starch.
Lugol’s
Click on the test tube rack
to get a clean test tube
Glucose
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Click on a fresh
eyedropper from the shelf
to add distilled water to
the test tube.
Lugol’s
Glucose
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Next click on the
eyedropper in the Lugol’s
solution to add a few
drops to test for starch.
Lugol’s
Glucose
Record your results.
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Next we will open the dialysis
tubing and fill it with about ½ full
of starch solution and about ½
full of glucose solution.
Lugol’s
Leave enough of the tubing so
that you can tie the end shut.
Glucose
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Click on the dialysis tubing in the
distilled water beaker to remove
it so that it can be opened.
Lugol’s
Next click on the starch or
glucose solution to fill the
dialysis tubing.
Glucose
H2O
Glucose
Starch
Starch
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Instructions on the Blackboard
Next click on the
yellow string to tie the
top of the dialysis
bag.
Lugol’s
Glucose
H2O
Starch
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Instructions on the Blackboard
Now click on the dialysis bag to
insert it into the distilled water.
Leave the dialysis bag in the
distilled water for 30 minutes.
Lugol’s
Click the start button on the
timer.
Glucose
H2O
Starch
START
00:00
30:00
25:00
20:00
15:00
10:00
05:00
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Instructions on the Blackboard
Remove the dialysis bag by
clicking on it.
Open one end of the dialysis
tubing by clicking on the yellow
string holding one end together
Lugol’s
Glucose
H2O
Starch
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Instructions on the Blackboard
Click on the test tube rack to
obtain a test tube.
We will add a small amount of
solution from the dialysis
tubing to the test tube to test
for glucose and starch.
Lugol’s
Glucose
H2O
Starch
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Instructions on the Blackboard
Click on one of the blue
eyedroppers on the shelf to add
solution from the dialysis tubing.
Lugol’s
Next click on the one of the
glucose test tapes to test for
glucose.
Glucose
Record your results
H2O
Starch
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Instructions on the Blackboard
Now we can test for starch by
using a few drops of Lugol’s
solution.
Lugol’s
Click on the eyedropper in the
Lugol’s solution to add to the
dialysis tube solution.
Glucose
Record your results.
H2O
Starch
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Instructions on the Blackboard
We will now perform the same
tests for glucose and starch on the
solution of distilled water in which
the dialysis tubing soaked for 30
minutes.
Lugol’s
We will need a clean test tube.
Click on the test tube rack.
Glucose
H2O
Starch
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Instructions on the Blackboard
Click on one of the blue
eyedroppers on the shelf to add
solution from the distilled water.
Lugol’s
Next click on the one of the
glucose test tapes to test for
glucose.
Glucose
Record your results
H2O
Starch
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Instructions on the Blackboard
Now we can test for starch by
using a few drops of Lugol’s
solution.
Lugol’s
Click on the eyedropper in the
Lugol’s solution to add to the
distilled water.
Glucose
Record your results.
H2O
Starch
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Instructions on the Blackboard
Click on the link
below to answer
questions on part 2 of
experiment # 3.
Click Here to Answer
Questions 1 - 6
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Instructions on the Blackboard
When you are finished with part 2 of
experiment # 3, be sure that you include the
following with your lab report.
Table of Dialysis Tests
Answers to Questions (1 - 6)
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At this point you have
finished experiment # 3, Parts
1 and 2 for this lab.
Would you like to end your
session or continue to
another experiment?
End this Session
Continue to Experiment #1
Continue to Experiment #2
Questions
1) Considering tonicity how would you describe the
relative tonicities of the, a) dialysis bag solution, and
b) beaker solution?
2) By analyzing the differences between the tonicities of
the solutions in the bag and the beaker, where should
water diffuse to, a) into the bag, or b) into the beaker?
3) Did starch diffuse from the bag? Why or why not?
4) Did glucose diffuse from the bag? Why or why not?
5) Did osmosis occur during this experiment? Why or
why not?
6) Did dialysis occur during this experiment? Why or why
not?
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Experiment #3
Questions
1) Over the 90 minute period, what distance did the column of
sugar move?
2) Which term is used to describe the tonicity of the distilled
water? (Hypotonic or Hypertonic)
3) Explain why the sugar solution rises in the thistle tube over
time.
4) Explain why the diffusion rate of water changed over the 90
minute period of time.
5) We began the experiment by pouring a 20% sucrose solution
into the thistle tube. Describe what the makeup of the sucrose
solution probably is after the 90 minute period. (more or less
than 20%).
6) Describe why this change in sucrose % has changed.
7) From the knowledge you have gained could you explain why it
is not a good idea to drink salt water when you are thirsty.
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Experiment #3
Drinking Salt Water
Drinking water normally quenches your thirst. But when you
drink salt water it seems to make you more thirsty. The
water in your mouth creates a situation in which the cells in
your mouth are in a hypertonic solution. In order to reach an
equilibrium, a net water movement out of the cells takes
place. Now the cells have even less water than before, and
you feel even more thirsty.
Salt water not only dries out your mouth but the cells in
your body too! As it enters your body, the cells near it
release water to reach equilibrium with the surrounding
fluid. The cells shrink and may become damaged. This is a
condition called dehydration, or excessive water loss.
In order to make ocean (salt) water drinkable, a system has
been devised to remove the salt. It is called distillation.
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Questions
Graph of Osmotic Potential vs Time
40
36
32
Measure
28
of mm
24
20
16
12
8
4
15
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Experiment #3
30
45
60
75
90
Minutes
Click Here To View a Printable
Version of This Table
Graph of Osmotic Change vs Time
8
7
6
Movement 5
in mm
4
3
2
1
15
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Experiment #3
30
45
60
75
90
Minutes
Click Here To View a Printable
Version of This Table
Graph of Osmotic Potential vs Time
40
36
32
Measure
28
of mm
24
20
16
12
8
4
15
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Experiment #3
30
45
60
Minutes
75
90
Graph of Osmotic Change vs Time
8
7
6
Movement 5
in mm
4
3
2
1
15
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Experiment #3
30
45
60
Minutes
75
90
Table of Osomotic Potential and Time
Time
0
15
Osmometer reading
3
10
*Movement in mm
7
30
45
60
75
90
*To calculate movement in mm you will need to subtract
the preceding value from the succeeding value
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Experiment #3
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Printable Version of This
Table
TABLE OF DIALYSIS TESTS
You should indicate a positive or negative
test for each of the solutions and tests in
the spaces provided
Glucose
Test Tape
Lugol’s
Solution
Glucose Solution
Starch Solution
Dialysis Tube Solution After
Soaking in Distilled Water
Beaker of Distilled Water Before
Insertion of Dialysis Tube
Beaker of Distilled Water After
Insertion of Dialysis Tube
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Experiment #3
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Version of the Table