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Cells
OSMOSIS
Aims:
 Compare hypotonic and hypertonic solutions
 Describe and differentiate types of passive transport
 Predict and explain the effects of osmosis on cells
Agenda:
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T&T
Diagram Debrief
Concept Map
Test Wizard Passive Transport Check
Egg Demo
Activity 5.5
Extension (free-response and POS 5.5)
Test Wizard
Engage: IV/Salty food/Finger…Elicit that all relate to osmosis, a type of passive transport in cells.
Explain:
Debrief diagrams in Do Now for following points
 Difference between iso/hypo/hyper
 Similarities and differences in types of passive transport
 Show water and food color as a quick demo to elicit high to low concentration and no energy.
 Concept map
 Poll
Explore
Effects of Osmosis on Egg Cells
 Explain that now we will focus on osmosis and how it affects cells
 Students observe demos and explain after seeing exemplar
 Students use Mybiology Activity 5.5 or below links to explain
o http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/dif.swf
o http://www.coolschool.ca/lor/BI12/unit4/U04L06/rbc.html
 Remind that often water moves rather than large solute which can’t pass through membrane.
 Show pp. 1-2 of MyBiology 5.5 if further explanation needed
Extend
 Predicting effects on cells in table
 Osmosis scenarios
 POS 5.5
Exit Slip: MC questions
Homework: Active Transport Annotation
Cells
OSMOSIS
Do Now
1.
Which area, X or Y, is more concentrated? Explain.
X
Y
2. Label each SOLUTION as hypo-, iso- or hypertonic compared to the cell. Briefly explain your
choices.
Solution
Solution
Cell
Solution
Cell
Cell
3. Give a caption to and annotate each diagram below.
Solute
4. What do all of the processes shown above have in common?
Cells
OSMOSIS
Exploring & Explaining Osmosis
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In this demo, one egg was placed in a hypotonic solution (0.0 M, or pure water) and another egg
was placed in a hypertonic solution (0.6 M sucrose).
Working in pairs, explain what occurred to each egg cell using your knowledge of osmosis.
Watch MyBiology Activity: Osmosis and Water Balance in Cells (5.5) pp.3-4 for help.
Solution in Beaker
What happened to the egg cell?
Why did this happen?
Isotonic (0.3 M)
The egg cell did not change in
In an isotonic environment the concentration
size .
of water and solutes inside the cell is the same
as the solution outside. This is equilibrium, and
no overall water movement by osmosis occurs.
Hypotonic (0.0 M)
Hypertonic (0.6 M)
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If time, check out the following links for more effects of osmosis on plants and animals:
o http://www.coolschool.ca/content/showcase.php?type=science
o http://www.biology.ualberta.ca/facilities/multimedia/uploads/alberta/dif.swf
Rules of Osmosis
Cells
OSMOSIS
Extending Osmosis
1. Complete the table below.
Environment
Plant cell
Animal cell
Plant cell
Animal cell
Plant cell
Plant cell
Animal cell
Water concentration is highest in…
Water will…
Cell will …
Hypotonic
Hypertonic
Hypertonic
Hypotonic
Isotonic
Hypertonic
Hypotonic
2. In the winter when roads are salted, plants that grow along the road often
die. Explain why using concentration, cells, water, low, high, osmosis.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
3. Explain why you feel thirsty after eating very salty or very sweet foods using the terms
concentration, cheek cells, low, water, high, osmosis in your explanation.
_______________________________________________________________________________________________
_______________________________________________________________________________________________
_______________________________________________________________________________________________
_______________________________________________________________________________________________
4. Hospital patients that are hooked up to an IV receive a slightly saline (salty) solution rather than
pure water. Explain why using the terms concentration, cells, low, water, high, osmosis in your
explanation.
_______________________________________________________________________________________________
_______________________________________________________________________________________________
_______________________________________________________________________________________________
_______________________________________________________________________________________________
5. When a person soaks in a bath tub for a long time, their fingers swell and wrinkle. Explain why using
the terms concentration, cells, low, water, high, osmosis.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
6. Complete Process of Science: How Does Osmosis Affect Cells? (5.5) at MyBiology.com
Cells
Exit Slip
OSMOSIS
Cells
OSMOSIS
Animation Guided Questions
Go to http://www.northland.cc.mn.us/biology/Biology1111/animations/passive1.swf
1. What is passive transport, in your own words?
2. What are three types of passive transport?
Tour the Cell membrane…
3. Why is it important that the membrane is fluid?
4. What kinds of molecules don’t pass easily through the lipid bilayer?
5. What kinds of molecules pass easily through the lipid bilayer?
Continue to Simple Diffusion…
6. What is diffusion?
7. In which direction (hi to low or low to hi) do molecules moves along a concentration gradient?
8. When does diffusion end?
9. What does equilibrium mean?
Continue to Facilitated Diffusion
10. Does diffusion require energy (ATP)?
11. Who “helps” certain molecules through the membrane?
12. How is facilitated diffusion similar to simple diffusion?
13. How is facilitated diffusion different from simple diffusion?
Continue to Osmosis
14. How is osmosis similar to diffusion?
15. How is it different from diffusion?
16. What is the difference between a hypertonic solution and a hypotonic solution?
17. Water will travel by osmosis from a __________________ environment to a __________________
environment. Why does this happen, based on the principle of diffusion?
18. Water is polar. Why is it able to pass through the nonpolar lipid membrane?
Cells
OSMOSIS
Notes
Passive Transport is the movement of molecules from _______ to _______ concentration without
_______________. A solution where molecules are evenly distributed is at _________________________.
3 Types of Passive Transport
1. Diffusion is the movement of _________________ from ______ to ______ concentration without
______________. Molecules that are ___________ or ___________ can diffuse across the lipid bilayer.
2. Osmosis is the movement of _________________ from _____ to _____ concentration without _____________.
Osmosis is a specific type of _______________. During osmosis, water travels from a _____________________
solution to a ______________________ solution.
a. Plant cells in hypertonic solution will _____________ because water ____________ the cell.
b. Plant cells in a hypotonic solution will ____________ because water ____________ the cell.
c. Plant cells in an isotonic solution will remain _____________ because water ___________ and
_______________ the cell.
d. Animal cells in a hypertonic solution will ________________ because water ____________ the cell.
e. Animals cells in a hypotonic solution will ____________ because water ____________ the cell.
f. Animal cells in an isotonic solution will _________________ because water ___________ and
_______________ the cell.
3. Faciliated diffusion is the movement of molecules from _________ to ________ concentration with the
help of ____________________. Molecules that are _____________ and ____________ cross the membrane this
way.
Practice
1. Identify the type of passive transport that occurs in each example.
_____________________ Water enters plant cells
_____________________ The odor of cologne spreads across a room.
_____________________ Tea from a tea bag spreads through a cup of hot water.
_____________________ Sugar enters the cell without energy but with the help of a protein
Cells
OSMOSIS
_____________________ Water leaves cheek cells when you eat salty food.
_____________________ Amino acids enter the cell without energy but with the help of a protein
_____________________ Food coloring spread through a glass of water
_____________________ Water leaves a red blood cell
2. Complete the Venn diagram using the following terms:
Passive
Water
Proteins
No energy
Large molecules
High to Low
Cells
Food coloring
Diffusion
Odor
Small molecules
Nonpolar molecules
Plasmolysis
Osmosis
2. In the diagrams below, assume that the solute can pass through the cell membrane. Label the areas of
high and low concentration of solute. Then use arrows to show the direction that the solute particle will
move during diffusion.
3. In the diagrams below, assume that the solute cannot pass through the cell membrane. Label the
areas of high and low concentration of water molecules. Then use arrows to show the direction that
water will move during osmosis.
Cells
OSMOSIS
3. Predict what will happen to each cell in the given conditions.
Environment
Plant cell
Animal cell
Plant cell
Animal cell
Plant cell
Plant cell
Animal cell
Where is water
concentration
highest?
Water will…
Cell will …
Hypotonic
Hypertonic
Hypertonic
Hypotonic
Isotonic
Hypertonic
Hypotonic
4. Complete the table below. Draw arrows to show the direction of water flow when necessary.
What is happening to the
Is water entering or
Where is water
cell?
leaving the cell?
concentration highest?
Cells
OSMOSIS
5. Complete the table showing the effects of osmosis on plant cells.
Does water
enter or leave?
What is happening to the
cell?
Where is the concentration of
water the highest?
Cells
OSMOSIS
6. A laboratory technician places red blood cells into three different solutions. Observations are recorded
each minute for five minutes.
Cells
OSMOSIS
A. In solution 1, is the concentration of solvent higher inside or outside the cell initially?
B. In solution 1, why did the cells disappear?
C. In solution 2, is the concentration of solvent higher inside or outside the cell initially?
D. In solution 2, why was there no change in the cells?
E.
In solution 3, is the concentration of solvent higher inside or outside the cell initially?
F.
In solution 3, why did the cells disappear?
G. What process explains the changes that occurred in these cells?
H. Which of the following best explains what is causing the red blood cells in solution 1 to
change size over the five-minute period?
a. Solvent is entering the cells faster than it is leaving the cells.
b. Solute is entering the cells faster than it is leaving the cells.
c. The cells are making new protein.
d. The cell’s membranes are dissolving.
I.
The laboratory technician concludes that red blood cells cannot function in any fluid
except serum. Which of the following best characterizes this conclusion?
a. It is accurate on the basis of the information given.
b. It is accurate because the cells changed in all the solutions but one.
c. It is inaccurate because the cells were outside the body.
d. It cannot be substantiated with the data provided.
Exit Slip
Under what conditions will a substance be likely to enter a cell through diffusion?
a. when the substance is a particle of food
b. when a molecule of the substance is very large
c. when the concentration of the substance is greater outside the cell than inside
d. when the concentration of the substance is greater inside the cell than outside
Cells
OSMOSIS
Do Now
1. Identify three types of diffusion.
2. What do the three types have in common?
3. Label the solute and solvent. Then draw arrows the direction that the solute particles will move
during diffusion.
4. Label where the solute is hypotonic and hypertonic. Then label where water concentration is high
and low. Then draw arrows to show the direction water would travel during osmosis (assume the
solute cannot cross the membrane.
Cells
OSMOSIS
Application Questions
Cells
OSMOSIS
Diffusion Experiment
Critical Concepts:
1. What do starch and glucose have in common?
2. How are starch and glucose different?
Problem: How does the size of solute affect transport across a semi-permeable membrane?
Hypothesis:
Materials:
 Dialysis Tubing
 Beaker
 Glucose/Starch solution
 Water
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Iodine
Pipet
Glucose Test Strips
Funnel
Experiment Design:
1. Obtain a piece of dialysis tubing that has been soaked in water.
2. Roll the tubing between your fingers to open it.
3. Close one end of the tube by knotting it.
4. Using a funnel and graduated cylinder, place 15 mL of glucose/starch solution in the dialysis bag.
5. Smooth the top of the bag to expel air and tie off the open end, leaving enough room to allow
for expansion.
6. Measure 160 mL distilled water into a beaker.
7. Add 4 mL of starch indicator solution (iodine) to beaker.
8. Place bag in beaker containing water and iodine.
9. Wait 30 minutes.
10. Test contents of bag and beaker for presence of starch (black color change) and glucose (green
color change on test strip.
Data:
Before
After
Cells
Location
Bag
Beaker
OSMOSIS
Starch Initial
Starch Final
Glucose Initial
Glucose Final
Results and Conclusions:
1. What represented the cell membrane in this experiment? Why?
2. Which substances (water, iodine, glucose, starch) diffused out of the bag? How do you know?
Why did this happen?
3. Which substances (water, iodine, glucose, starch) diffused into the bag? How do you know? Why
did this happen?
4. Which substances (water, iodine, glucose, starch) did not diffuse? How do you know? Why did this
happen?
5. How do your results compare with your hypothesis? Was it supported or rejected? Use evidence to
support your answer.
6. Based on your experiment, what is the relationship between size of solute and ability to diffuse
across a semi-permeable membrane?
Cells
OSMOSIS
Do Now
1. A laboratory technician places red blood cells into three different solutions. Observations are
recorded each minute for five minutes.
A. In solution 1, is the concentration of solvent higher inside or outside the cell initially?
B. In solution 1, why did the cells disappear?
C. In solution 3, is the concentration of solvent higher inside or outside the cell initially?
D. In solution 3, why did the cells disappear?
E. What process explains the changes that occurred in these cells?
F.
Which of the following best explains what is causing the red blood cells in solution 1 to
change size over the five-minute period?
a. Solvent is entering the cells faster than it is leaving the cells.
b. Solute is entering the cells faster than it is leaving the cells.
c. The cells are making new protein.
d. The cell’s membranes are dissolving.
G. The laboratory technician concludes that red blood cells cannot function in any fluid
except serum. Which of the following best characterizes this conclusion?
a. It is accurate on the basis of the information given.
b. It is accurate because the cells changed in all the solutions but one.
c. It is inaccurate because the cells were outside the body.
d. It cannot be substantiated with the data provided.
2. Under what conditions will a substance be likely to enter a cell through diffusion?
a. when the substance is a particle of food
b. when a molecule of the substance is very large
c. when the concentration of the substance is greater outside the cell than inside
d. when the concentration of the substance is greater inside the cell than outside