Membrane Permeability
012-10971 r1.04
Membrane Permeability
Introduction
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or print your journal to turn in your
work.
Each page of this lab that
contains the symbol
should be inserted into your
journal. After completing a
lab page with the snapshot
symbol, tap
(in the
upper right hand corner) to
insert the page into your
journal.
Note: You may want to take a
snapshot of the first page of
this lab as a cover page for
your journal.
Membrane Permeability
Lab Challenges
What types of substances are able to pass through a semi-permeable membrane?
Membrane Permeability
Background
• The contents of a cell are separated from the outside environment by a
membrane.
• The cell membrane, also called plasma membrane, consists mostly of
phospholipids and proteins. Phospholipids have 2 distinct regions: a hydrophilic
head and a hydrophobic tail. They form a bilayer by arranging themselves tail to
tail, so only their hydrophilic heads are exposed to the aqueous environment
inside and outside the cell.
Membrane
Permeability
Self
Check
Self Check
1. Phospholipids arrange themselves in a bilayer
because they have ____________________.
a) hydrophobic tails and hydrophilic heads
b) hydrophilic tails and hydrophobic tails
c) opposite charges
d) bipolar DNA
This image is a reminder to
tap
to take a snapshot
of the page after you have
entered your response.
Membrane Permeability
...Background
•
In some cases, the cell membrane acts as a passive barrier and substances can
move in and out of the cell based on concentration gradient. Water, carbon
dioxide, oxygen, cholesterol and other small polar molecules are able to diffuse
passively across the membrane.
•
In other cases the membrane can be very selective about what is able to enter
and leave. Substances that cannot diffuse through the membrane must pass
through a protein channel. Some protein channels act as an open gateway that
specific substances can pass through. Other protein channels require energy
input and act as pumps to move substances against the concentration gradient.
Membrane
Permeability
Self
Check
Self Check
2. Substances that cannot diffuse directly through the
phospholipid bilayer but go through a(n)
____________.
a) ion gate
b) water pore
c) carbohydrate chain
d) protein channel
Membrane Permeability
Safety
• Use all standard laboratory safety procedures.
• Wear safety glasses and lab coats or aprons.
• Dispose of chemicals and solutions as instructed.
Membrane Permeability
Materials and Equipment
Collect all of these materials before beginning the lab.
• pH sensor
• Beaker, 250 mL
• Large Base and Support Rod
• Utility clamp (2)
• Lugol's Iodine
• 0.1 M Hydrochloric Acid
• 0.1 M Sodium Hydroxide
•
•
•
•
•
•
•
Starch Solution
Dialysis Tubing, 15cm length (2)
Magnetic stirrer and stir bar
Wash Bottle
Distilled Water
Binder clip
String
Membrane Permeability
Sequencing Challenge
A. Record data and
then determine the
change in pH for
each data run.
B. Lower the dialysis
tubing into the
water.
C. Prepare the
dialysis bags.
D. Add distilled water
to the beaker and
turn on the
magnetic stirrer.
The steps to the left are part
of the procedure for this lab
activity. They are not in the
right order. Determine the
correct sequence of the
steps, then take a snapshot
of this page.
Membrane Permeability
Setup: Dialysis Bags (HCl and Starch)
Note: Wash your hands. The oils on your skin can clog the
pores of the tubing.
1. Tie one end of one piece of dialysis tubing with string
to create a bag. Rub the tubing between your fingers
to open the top of the bag.
2. Pour 15 mL of 0.1 M HCl (hydrochloric acid), and 5
mL of the starch solution into the bag.
Caution: HCl is corrosive and can ruin clothing, and cause skin
and eye irritation. Notify your teacher of any skin/eye contact.
3. Fold over the open end of the bag and use a binder
clip, or string, to secure it shut.
Membrane Permeability
Setup: Dialysis Bags (NaOH)
4. Tie one end of a second piece of dialysis tubing with string to create a bag.
Rub the tubing between your fingers to open the top of the bag.
5. Pour 15 mL of 0.1 M NaOH (sodium hydroxide).
Caution: NaOH is corrosive and can ruin clothing, and cause skin and eye irritation.
Notify your teacher of any skin/eye contact.
6. Fold over the open end of the bag and use a binder clip, or string, to secure it
shut.
7. Rinse both bags under a gentle stream of water and place aside on a labeled
paper towel.
Membrane Permeability
Setup: Hydrogen Ions
1. Connect a pH sensor to the SPARK Science Learning
System.
2. Place a spin bar into a 250 mL beaker and place the
beaker on the magnetic stirrer.
3. Use a base, support rod and clamp to position the pH
probe low in the beaker, but not touching the stir bar.
4. Use a second clamp to suspend the dialysis bag
containing the HCL and starch above the beaker.
5. Add 100mL of water and 25 drops of Lugol's iodine to
the beaker. Adjust the pH probe so it is in the water.
Membrane Permeability
Q1: What will happen to the
pH in the beaker when the
HCl bag is lowered into it?
Draw your prediction on
the graph provided*.
*To Draw a Prediction:
1. Tap
to open the tool
palette.
2. Tap
then use your finger
to draw your prediction.
3. Tap
when finished.
4. If you make a mistake, tap
to clear your prediction.
Membrane Permeability
Q2: Will the hydrogen
ions move out of the
bag? How will you
know if they do?
Q3: Will the starch
molecules move out
of the bag? How will
you know if they do?
Q4: Will the iodine
molecules move into
the bag? How will
you know if they do?
Membrane Permeability
Collect Data: HCl
1. Turn on the magnetic
stirrer.
2. Tap
to start collecting
data.
3. Wait 60 seconds and
lower the dialysis bag
into the water.
4. After 300 seconds, tap
to stop data collection.
Membrane Permeability
5. Enter any color change
observations in the data
table.*
*To Enter Data into a Table:
1. Tap
to open the tool
palette.
2. Tap
then tap a cell in
the data table to
highlight it in yellow.
3. Tap
to open the
Keyboard screen.
Membrane Permeability
Setup: Hydroxide Ions
1. Dispose of the HCl bag and clean out the 250 mL
beaker.
2. Place a spin bar into the beaker and place the beaker
on the magnetic stirrer.
3. Use a base, support rod and a clamp to position the
pH probe low inside the beaker, but not touching the
stir bar.
4. Use a second clamp to suspend the dialysis bag
containing the NaOH above the beaker.
5. Adjust the pH probe so it is in the water.
Membrane Permeability
Q5: What will happen to the
pH in the beaker when
the NaOH bag is lowered
into it? Draw your
prediction in the graph*.
*To Draw a Prediction:
1. Tap
to open the tool
palette.
2. Tap
then use your
finger to draw your
prediction.
3. Tap
when finished.
4. If you make a mistake,
tap
to clear your
prediction.
Membrane Permeability
Collect Data: NaOH
1. Turn on the magnetic
stirrer.
2. Tap
to start collecting
data.
3. Wait 60 seconds and lower
the dialysis bag into the
water.
4. After 300 seconds, tap
to stop data collection.
Membrane Permeability
Data Analysis
1. Determine initial pH,
final pH and the change
in pH for each run.*
Note: Enter these values on
the next page.
* To Find the X- and YValues of a Data Point:
1. Tap
to open the tools
palette.
2. Tap
and then tap a
data point.
3. Tap or to select
nearby data points.
Membrane Permeability
Data Analysis
2. Record initial pH, final
pH, and the change in pH
for each run in the table.
*To Enter Data into a Table:
1. Tap
to open the tool
palette.
2. Tap
then tap a cell in
the data table to
highlight it in yellow.
3. Tap
to open the
Keyboard screen.
Membrane Permeability
Analysis
1. Describe what happened to the pH in the beaker during the soaking of the HCl
bag. What does this indicate about the permeability of H+ ions to the membrane?
Membrane Permeability
Analysis
2. Describe what happened to the pH in the beaker during the soaking of the NaOH
bag. What does this indicate about the permeability of OH- ions to the membrane?
Membrane Permeability
Analysis
3. Describe what happened between the starch and iodine. Was iodine abe to move
into the bag? Was starch able to move out of the bag? Explain your answer and
support it with data.
Membrane Permeability
Analysis
4. This lab is demonstrating diffusion and semi-permeable membranes. Define these
concepts.
Membrane Permeability
Synthesis
1. How could the diffusion rate be increased?
Membrane Permeability
Synthesis
2. How could you use a series of molecules to determine the size of the pores in the
membrane?
Membrane Permeability
Synthesis
3. How does this membrane model differ from a real cell membrane? What
structures are present in a real cell membrane that regulate what can enter and
exit the cell?
Membrane Permeability
Synthesis
4. Does this model illustrate active or passive transport? Explain your answer.
Membrane Permeability
Multiple Choice
1. Despite differences in cell types, all cells have a
_________________.
a) cell wall
b) cell membrane
c) golgi apparatus
d) endoplasmic reticulum
Membrane Permeability
Multiple Choice
2. The membrane of a cell will allow water, oxygen,
carbon dioxide, and glucose to pass through.
However, other substances are blocked from
entering. This type of membrane is called:
a) semi-permeable
b) perforated
c) permeable
d) non-permeable
Membrane Permeability
Multiple Choice
3. Cell membranes are constructed mostly of
a) protein channels.
b) carbohydrate channels.
c) lipid bilayers.
d) hydrophobic regions
Membrane Permeability
Multiple Choice
4. Look at the diagram to the right and choose the
correct statement.
= starch
= glucose
The membrane is permeable to glucose, but not permeable
to starch
a)
b)
c)
d)
Glucose will move from right to left.
Starch will move from right to left.
Salt will move from right to left
No molecules will move in any direction.
Membrane Permeability
Congratulations!
You have completed the lab.
Please remember to follow your teacher's instructions for cleaning-up and submitting
your lab.
Membrane Permeability
References
Images are taken from PASCO documentation, public domain clip art, or Wikimedia Foundation Commons.
http://commons.wikimedia.org/wiki/Image:Semipermeable_membrane.png
http://www.freeclipartnow.com/office/paper-shredder.jpg.html
http://commons.wikimedia.org/wiki/File:Bilayer_scheme.svg
http://commons.wikimedia.org/wiki/File:Cell_membrane_detailed_diagram_3.svg