Today’s Class
 Review of Chapter 8.1 Membrane Properties
(small quiz).
 Lab: Transport across a semi-permeable
membrane
 Passive transport: OSMOSIS
 Lab Conclusion: Observation and results
8.2 Transfer Across Cell
Membranes
1 Molecules crossing the cell membrane are
distinquished by 3 things?
2 All matter is in a constant state of motion. The
amount (rate) of motion is dependent on?
3 Motion of particles results in a net movement
toward areas of lower concentration of those
particles. The difference in concentration
between two areas is called a?
Diffusion Lab: 8.2 – part A
 This lab will reinforce what we have learned about
passive transport across semi-permeable membranes
 Please work in bench groups of 4
 Please practice SAFE LAB PROCEDURES!
 Each student must hand in a description and
explanation of any movement you observed. The
description may be in the form of a data table.
3
Diffusion Lab: 8.2 – part A
Purpose: To investigate diffusion (Passive
Transport) across a semi-permeable membrane.
Materials: Rubber gloves, safety goggles, lab
apron, 500ml beaker, tap water (300ml), 1 10cm dialysis tube, 2 elastics, paper towels,
starch solution, plastic spoon, iodine solution
(Lugol’s).
4
Procedure:
1. One person from each group will gather the materials.
Carry the materials in a safe manner.
2. Pour 300ml of lukewarm tap water into the 500ml beaker.
3. Submerge the 10cm dialysis tube into the water for 1-2
minutes. Remove the tube and constrict one end of the tube
using an elastic.
4. Add a few drops of the iodine solution to the beaker of
water so the colour of the water is pale yellow.
5. Open the other end of the tube by rolling it between your
fingers. Using the plastic spoon, gently scope the starch
solution into the tube until it is ¾ full.
5
Procedure:
6. Constrict this end of the tube using an another elastic
7. Wash the sealed tube off under gently running
lukewarm water. Pat dry the tube with paper towels.
8. Weigh the tube and it’s contents. Record the initial
mass in your group table.
9. Submerse the tube in the beaker. Add more water if
needed. Let the product sit for 25 minutes.
6
1
2
3
4
7
Data table
Mass of
Volume
tube and of water
starch
in the
beaker
Initial
Final
Colour of Colour of
water
tube
Chapter 8 Dynamic Cells
http://kentsimmons.uwinnipeg.ca/cm1504/Image127.gif
Passive Transport
 Movement of materials across membranes
without the input of energy is called passive
transport.
 There are 3 types of passive transport
1. Diffusion
2. Osmosis
3. Facilitated diffusion
1. Diffusion
http://www.williamsclass.com/SeventhScienceWork/ImagesCellBricks/Diffusion.gif
http://gotoknow.org/file/somluckv/Cell_membrane02.jpg
Diffusion Across Membranes
 Molecules diffuse across cell membranes.
 Very small molecules can move between the
phospholipid molecules from one side of the
membrane to the other.
 Cells do not expend any energy during this
process.
 Eg: O2 is always being used by the cell the
concentration of O2 is always lower inside the cell
compared to outside the cell.
2. Osmosis – Diffusion of
Water
 Most of the molecules that fill and
surround cells are water (H2O).
 The diffusion of water across a
membrane is called osmosis.
Osmosis – Diffusion of Water
http://i77.photobucket.com/albums/j48/annahybrid/normal_osmosisweb.jpg
Osmosis – Diffusion of Water
 Water molecules move from areas of
high concentration of water to areas
of low concentration of water across
a semi-permeable membrane.
Osmosis
http://www.biologycorner.com/resources/osmosis.jpg
Osmosis
Passive Diffusion of Water
 If one solution has a high concentration
of H2O and a low concentration of
solutes relative to another solution it is
called HYPOTONIC.
Hypotonic
http://www.williamsclass.com/SeventhScienceWork/ImagesCellBricks/hypertonic.jpg
Osmosis
Passive Diffusion of Water
 If one solution has a low concentration of
H2O and a high concentration of solutes
relative to another solution it is called
HYPERTONIC.
Hypertonic
http://www.williamsclass.com/SeventhScienceWork/ImagesCellBricks/hypotonic.jpg
Osmosis
Passive Diffusion of Water
 If the concentration of water is equal on
both sides of a membrane the solutions
are called ISOTONIC.
Isotonic
http://www.williamsclass.com/SeventhScienceWork/ImagesCellBricks/isotonic.jpg
Osmosis in Living Cells
 Maintaining water balance across the cell
membrane is essential to survival.
 If the concentration of water outside the cell is
greater than inside the cell water will flow into
the cell (cells in distilled water).
Water Movement
A
C
B
D
http://www.kscience.co.uk/resources/ks5/as/cells/osmosis/Plasmolysis_and_recovery.jpg
Osmosis in Living Cells
 In plant cells, the
cell’s contents
swell (turgid) but
the cell walls keep
the cell from
exploding.
http://leavingbio.net/OSMOSIS%20AND%20DIFFUSION_files/image021.gif
Osmosis in Living Cells
 In animals cells,
(with no cell wall)
the cell will explode
or rupture.
http://www.wadsworth.org/chemheme/heme/cytoheme/hemepix/slide092.jpg
Osmosis in Living Cells
 If the concentration of water outside
the cell is less than inside the cell,
water will flow out of the cell (cells in
salt water)
Osmosis in Living Cells
 In plant cells, the cell contents will lose
water, shrivel and pull away from the cell
wall (plasmolysis).
 In animals cells (no cell wall) the cell
contents will lose water and shrivel
(crenated)
Crenated Red Blood Cells
http://labmed.hallym.ac.kr/hematol/Hematol-Cell-Lists/crenatedrbcs.jpg
Membranes at Work
 Water Purification
 Reverse osmosis
 Water is filtered, by pressure, through a membrane
with pores that only allow water through.
 All substances larger than water cannot pass
through
 These systems are used in houses where well
water is too salty or larger systems can provide
clean water during disasters or war.
http://enr.construction.com/images2/2005/08/050815-20.jpg
Membranes at Work
 Kidney Dialysis
 Blood is pumped through a synthetic semi-permeable
tubing called dialysis tubing.
 The dialysis tubing is immersed in a saline solution similar
to blood.
 Wastes in the blood move from the tubing into the solution
by diffusion.
 Because the salts and water are in equilibrium with the
blood, there is no loss of salts and water from the blood.
http://biomed.brown.edu/Courses/BI108/BI108_2008_Groups/group04/images/ppf/girl.png
Membranes at Work
 Controlled delivery of medication.
 Semi-permeable membranes deliver medications in a safe,
controlled manner.
 Transdermal patches on the skin use a semi-permeable
membranes to deliver the medication at a constant rate.
 This delivery method is used to deliver drugs that counter
motion sickness, and nicotine to aid in stopping smoking.
 Artificial vesicles called Liposomes can be used to
transport medicines to specific sites in our bodies.
Test Questions: TRUE or FALSE?
1. The amount (rate) of motion is dependent on the
nature of particles, its state (gas, solid, liquid), and
temperature.
2. Movement of materials across membranes with the
input of energy is called passive transport.
3. In a crenated cell the turgor may cause the cell to
swell and rupture.
4. If one solution has a low concentration of H2O and a
high concentration of solutes relative to another
solution it is called HYPERTONIC.
Water molecules move from areas of _______
concentration of water to areas of _______
concentration of water across a semi-permeable
membrane to maintain a (an) ______ condition.
A. High; Low; Hypertonic
B. Low; High; Hypotonic
C. High; Low; Isotonic
D. Low; High; Isotonic
Diffusion Lab: 8.2 – part B
 Observe the colour of the water in the beaker and the
colour of the dialysis tube. Record observations on the
data sheet.
 One student weighs the tube and another records it on
the data sheet. Students to take note of any change in
mass to help answer the lab questions.
 As a group they are to complete 3 questions on the back
of the data sheet and submit at the end of the class.
38
Data table
Mass of
Volume
tube and of water
starch
in the
beaker
Initial
Final
Colour of Colour of
water
tube
Diffusion Lab: Questions
As a group, answer all questions on the back of your
group’s Data Sheet. Submit at the end of the class
1. Is iodine moving through the membrane osmosis
or diffusion?
2. Did the water move into the dialysis tube through
the membrane? How can you explain this?
3. Did the starch move out of the dialysis tube
through the membrane? How can you explain this?
40
Next Class
 Review of Chap. 8.2 Transport Across Cell
Membrane
 Introduction of the next lesson: Facilitated
Diffusion