Name _______________________________ Date __________________ Period __________
Diffusion and Osmosis and Tonicity
1. What is diffusion?
Movement of molecules from high concentration to a lower concentration.
2. What is facilitated diffusion?
Molecules move down a concentration gradient (high to low) with the aid of special proteins
(Channel or carrier proteins)
3. What is osmosis?
Diffusion of water across a semipermeable membrane from an area of high water concentration to
an area of low water concentration.
4. In which direction does water move across membranes, up or down the concentration gradient?
______Down_____________
5. Define these 3 terms:
a. isotonicb. hypertonic
c. hypotonic
6. Use arrows to show the direction of water movement into or out of each cell. Label the cell in an
isotonic environment, a hypotonic environment, and a hypertonic environment.
Moving out of the cell
Moving in both directions
Moving into the cell
Hypertonic Solution
Isotonic Solution
7. Match the description or picture with the osmotic condition:
A. Isotonic
Hypotonic Solution
__C___ solution with a lower solute concentration
___A__ solution in which the solute concentration is the same
B. Hypertonic
__C___ condition plant cells require
___A__ condition that animal cells require
C. Hypotonic
__C___ red blood cell bursts (cytolysis)
___B__ plant cell loses turgor pressure (Plasmolysis)
__B___ solution with a higher solute concentration
___C__ plant cell with good turgor pressure
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__C___ solution with a high water concentration
8. Draw the arrow for the MOVEMENT OF WATER and LABEL the tonicity for each solution
(isotonic, hypotonic, or hypertonic):
9. Describe what will happen to the glucose, the sucrose, and the water in this U-Tube.
a) What will happen to the glucose? Why?
b) What will happen to the sucrose? Why?
c) What will happen to the water? Why?
Diffusion and Osmosis Problems:
1.) If a cell (with no dye in it) is in a solution of 10% dye molecules and the dye can cross the cell’s membrane,
what do you predict will happen to the dye? Go into the cell
2.) If a cell (with 3% alcohol in it) is in a solution of 10% alcohol molecules and the alcohol can cross the cell’s
membrane, what do you predict will happen to the alcohol? Go into the cell
3.) If a cell (with 10% oxygen in it) is in a solution of 3% oxygen molecules and the oxygen can cross the cell’s
membrane, what do you predict will happen to the oxygen? Go out of the cell
4.) You have a cell, with a semi permeable membrane and a 1.5% potassium concentration. You put it into a
solution of 2% potassium. What type of solution is it in? What direction would you expect water to flow?
What do you expect to see happen to the cell? Hypertonic solution, Out of the cell, Shrink/Shrivel (Plasmolysis)
5.) You have a cell, with a semi permeable membrane and a 1.5% potassium concentration. You put it into a
solution of 1.05% potassium. What adjective describes the solution? What direction would you expect water to
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flow? What do you expect to see happen to the cell? Hypotonic solution, Into the cell, Get bigger
(Cytolysis/Turgid)
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