Osmosis Tiered Lesson

Name: ________________________________________ Period: ___ Date: ____________________
Osmosis Worksheet-Straight Ahead
Introduction. The cell membrane is a semi-permeable structure. Semi-permeable means that some - but not all - particles can
move freely through the membrane barrier without using energy. Large, complex molecules like proteins and carbohydrates,
are too large and cannot move through the membrane without energy. Water, however, can move freely through the membrane
using a type of diffusion called osmosis.
Storyboard #1: The image below demonstrates what happens to a cell when placed in a solution of sugar and water.
1. Compared to the Initial cell, the Final cell looks much different. Keeping in mind the information provided in the
introduction, what do you think caused the cell to change shape?______________________________________
___________________________________________________________________________________________
Storyboard #2: The image below demonstrates what the molecules were doing inside and outside the cell from Question #1.
Inside cell
Cell
Membrane
Outside Cell
Initial Intermediate Final
Hypotonic
(Least sugar concentration)
(Greatest sugar concentration)
Hypertonic
Initial
Intermediate
Key: Water: Sugar:
2. Using the storyboard above, describe what happed to the cell from Question #1 at the particle level.
_________________________________________________________________________________________________
` _________________________________________________________________________________________________
Final
3. The environment on the inside of the cell has a different sugar concentration than the outside of the cell. In each
picture, identify which side of the cell membrane (external or internal) has the greatest concentration of sugar. The first
one has been done for you as an example.
4. The internal and external environments of the cell can be compared using the following terminology – hypertonic,
hypotonic, and isotonic. Define these terms in your own words below. Then label the internal and external
environments in each of the pictures using the terms you defined. The first one has been done for you as an example.
Hypotonic: _______________________________________________________________________________
Isotonic: _______________________________________________________________________________
Hypertonic: _______________________________________________________________________________

Storyboard #3
Observe the completed portion of the storyboard below. Identify the internal and external solutions as isotonic, hypotonic or
hypertonic in the initial, immediate, and final stages. Then write a one sentence explanation about what occurred between the
two molecules.
Internal
Cell
Membrane
External
Key: Water: Sugar:
5. This is what I think is happening:___________________________________________________________________
Storyboard #4
Internal
Cell
Membrane
External
Key: Water: Salt:
6. This is what I think is happening:__________________________________________________________________
Discussion Questions
Initial
Initial
Intermediate
Intermediate
7. Based on what you have completed in this investigation, explain what “diffusion of water” means. __________________
_________________________________________________________________________________________
8. Living systems try to maintain homeostasis. Define homeostasis, and then explain how the cells in your storyboard
reached homeostasis. _______________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
9. Based on what you observed in storyboard on question #5, describe how the sugar and water behave once they reach
equilibrium. ________________________________________________________________________________________
__________________________________________________________________________________________________
10. The explanation below was made by a student after observing Storyboard #3.
“I think the water molecules are moving in to make the numbers of particles
equal on both side of the cell membrane.”
Evaluate whether this statement is true or false. Then, justify your answer.
__________________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
Final
Final

Name: ________________________________________ Period: ___ Date: ____________________
Osmosis Worksheet - Uphill
Introduction. The cell membrane is a semi-permeable structure. Semi-permeable refers to the property which allows some - but
not all - particles to move freely through the membrane barrier without the assistance of energy. Large, complex molecules like
proteins and carbohydrates are too large and cannot penetrate this barrier unless energy is present. Water, however, can move
freely through the membrane using a diffusive process called osmosis.
Storyboard #1: Shows over time what happens to a cell when placed in a solution of sugar and water.
1. Compared to the Initial cell, the Final cell looks much different. Keeping in mind the information provided in the
introduction, what do you think caused the cell to change shape?______________________________________
___________________________________________________________________________________________
Storyboard #2: The image below demonstrates what the molecules were doing inside and outside the cell from Question #1.
Inside cell
Cell
Membrane
Outside Cell
Initial Intermediate Final
Initial
Intermediate
Key: Water: Sugar:
2. Using the storyboard above, describe what happed to the cell in Question #1 at the molecular. Explain why you think this
occurred._________________________________________________________________________________________
` _________________________________________________________________________________________________
Final
3. The environment on the inside of the cell contains a different sugar concentration than the outside of the cell. In each
picture, identify which side of the cell membrane (external or internal) has the greatest concentration of sugar.
4. The internal and external environments of the cell can be compared using the following terminology – hypertonic,
hypotonic, and isotonic. Define these terms in your own words below. Then label the internal and external environments
in each of the pictures using the terms you defined.
Hypotonic: _______________________________________________________________________________
Isotonic: _______________________________________________________________________________
Hypertonic: _______________________________________________________________________________

Storyboard #3
Observe the completed portion of the storyboard below. Identify the internal and external solutions as isotonic, hypotonic or
hypertonic in the initial, immediate, and final stages. Then write a one sentence explanation about what occurred between the
two particles.
Internal
Cell
Membrane
External
Intermediate
Key: Water: Sugar:
5. This is what I think is happening:___________________________________________________________________
Storyboard #4
Complete the storyboard below showing how the particles will move in order to achieve equal internal and external saltwater
concentrations. Then record a one sentence summary telling what occurred in the storyboard.
Internal
Cell
Membrane
External
Initial
Initial
Intermediate
Key: Water: Salt:
6. This is what I think is happening:___________________________________________________________________
Discussion Questions
7. Osmosis is the diffusion of water. Identify another example of diffusion you have experienced firsthand and explain what
occurred in the process as it was happening. _____________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
8. Living organisms need to maintain a state of balance. What characteristic of life describes balance in an organism?
Explain how the cells in the storyboards achieved a state of balance. ___________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
9. Based on what you observed in storyboard on question #5, describe how the sugar and water behave once they reach
equilibrium. ________________________________________________________________________________________
__________________________________________________________________________________________________
10. The explanations below were made by two students after observing Storyboard #3.
DeAndre:“I think that the diagrams represent diffusion across the cell membrane and that the liquid is
hypertonic because the sugars don’t move across.”
Madison:“The water wants to move out of the cell by osmosis because there are fewer water molecules outside
the cell compared to inside.”
Which of the students are correct? DeAndre______ Madison______ Both______ Neither______
Explain your answer in paragraph format on an attached sheet of notebook paper.
Final
Final