Download OBSERVING OSMOSIS IN ELODEA

OBSERVING OSMOSIS IN ELODEA
Ojective: Observe the effects of fresh water & salt water on Elodea leaf cells to gain a better
understanding of osmosis.
Materials:
Compound microscopes
Clean microscope slides
Cover slips
Pipettes
Elodea
Fresh water
Salt
Beakers
Spoons
Paper towels
Colored pencils
Procedure:
1. Obtain a clean microscope slide. Make a wet-mount slide of Elodea using fresh water.
a. Place a drop of fresh water from beaker onto the center of slide.
b. Place a piece of elodea leaf onto the drop.
c. Put the cover slip on top of the water by placing the cover slip on the edge of the water at a
45-degree angle & slowly lower it. If you have any air bubbles, tap the cover slip, & use a
paper towel to remove excess water.
2. View the wet-mount under the microscope. Remember to start on the lowest power and then
move to a higher power, the medium objective will likely give you the best view.
a. Draw at least 5 plants cells in “Circle A” using colored pencils.
b. Label the cell wall and chloroplasts in “Circle A”
3. Remove the cover slip, and use a paper towel to blot off the fresh water.
4. Prepare a saline (salt) solution
a. Mix 2-3 spoonfuls of salt with 100 mL of tap water
5. Place a drop of the saline solution onto the Elodea leaf, and replace the cover slip (using the same
technique as before).
6. View the saline wet-mount under the microscope. Remember to start on the lowest power and
then move to a higher power, the medium objective will likely give you the best view.
a. Watch what happens to the chloroplasts and cell wall. It may take 1-2 minutes to see the
effects of the saline solution.
b. Draw at least 5 plants cells in “Circle B” using colored pencils.
c. Label the cell wall, cell membrane, chloroplasts in “Circle B”
7. Dispose/clean all materials.
a. Dispose of Elodea leaves in trash. Dispose of cover slips in glass box.
b. Rinse off slide and beaker with saline solution.
c. Clean your lab area, wash your hands, & then answer the analysis questions.
Name: ______________________________________ Period: __________ Date: _______________
Observing Osmosis in Elodea – Questions
All students must turn in analysis questions!
Circle A
Locate the cell wall & chloroplasts
Circle B
Circle C
Locate the cell wall, cell membrane, & chloroplasts
Show the movement of water
1. Where were the chloroplasts located in the Elodea leaf under normal conditions? (in the center, by
the cell wall, spread out?)
2. Where were the chloroplasts located in the Elodea leaf when the saline solution was added? (in the
center, by the cell wall, spread out?)
3. In which cell structure do you find the most water in a plant cell, such as the Elodea leaf? (Hint: which
organelle is used for storage and is larger in plant cells?)
4. Describe below what happened when you added the saline (salt) solution to the leaf. Draw an elodea
plant cell in “Circle C” and use arrows to show the movement of water. This is illustrating what
happened when you added the saline solution.
5. Why did water move in this direction? (Hint: think about the concentration of the salt solute inside & outside of
the plant cell. Look at your concentration gradient diagram you glued in your journal.)
6. In thinking about what you observed in this lab, what would happen to plants on the side of a road if
salt was sprayed to melt ice on the road?
MULTIPLE CHOICE
____ 1. Which of the following is a function of the cell membrane?
A. Breaks down lipids, carbohydrates, & proteins from foods
B. Regulates which materials enter & leave the cell
C. Stores water, salt, proteins, & carbohydrates
D. Keeps cell wall in place
____ 2. An animal cell that is surrounded by fresh water will burst because the osmotic pressure causes A. Water to move into the cell.
B. Water to move out of the cell.
C. Solutes to move into the cell.
D. Solutes to move out of the cell.
____ 3. Diffusion is the movement of particles (solute) from A. An area of low concentration to an area of high concentration.
B. An area of high concentration to an area of low concentration.
C. An area of equilibrium to an area of high concentration.
D. All of the above.
____ 4. The diffusion of water across a selectively permeable membrane is called A. Osmotic pressure
B. Osmosis
C. Facilitated diffusion
D. Active transport
____ 5. Even though conditions in the external environment vary widely, most organisms must keep internal
conditions, such as temperature and water content, fairly constant in order to survive. The process by
which they do this is called A. Cohesion
B. Symbiosis
C. Homeostasis
D. Permeability