Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
Background:
Diffusion of water molecules across a cell’s membrane from areas of high
water concentration to areas of low water concentration is called osmosis. This
movement of water may be harmful to cells. It can result in cell water loss
(plasmolysis) when living cells are placed into a hypertonic environment (where the
concentration of solute is higher outside the cell and lower inside the cell,
therefore, causing the concentration of water inside the cell to be higher than the
concentration of water outside the cell).
Most cells, however, live in an environment that is isotonic (with the solute
concentration being equal inside and outside of the cell, and therefore, the water
concentration also being equal on both sides of the cell membrane). Thus, under
normal isotonic conditions, there are no harmful effects to the cell.
Purpose:
In this investigation you will:
a. prepare a wet mount slide of an Elodea leaf in fresh water and a wet mount slide
of an Elodea leaf in salt water for observation using the microscope.
b. observe cells from both wet mounts and draw diagrams of each.
c. compare the appearance of normal Elodea cells in fresh water (an isotonic
environment) and plasmolyzed (shriveled) Elodea cells in salt water (a hypertonic
environment).
Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
Materials:
 microscope
 fresh/tap water (with dropper)
 (1) microscope slide
 ~5% salt water solution (with dropper)
 (2) coverslips
 tweezers/forceps
 Elodea (a freshwater plant)
Wet Mount Preparation Procedure:
fresh water
5% salt water
1. Prepare a wet mount using figure 1 as a guide:
a. Put an Elodea leaf on the right side of the slide.
i. Add 1 drop of salt water to the Elodea leaf on the right side of the slide.
ii. Put a coverslip over this leaf.
iii. Dry off any excess salt water on the remaining area of the slide.
b. Put an Elodea leaf on the left side of the slide.
i. Add 1 drop of fresh water to the Elodea leaf on the left side of the slide.
ii. Put a coverslip over this leaf.
c. Make sure that the salt water and the fresh water do NOT TOUCH! If
they do, clean everything off of your slide and start over using fewer
drops of water on each side.
d. Make sure that you don’t change the position of your slide (right should be
salt water and left should be fresh water).
Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
Observation of Elodea in FRESH water Procedure:
1. Observe the leaf on the left (in FRESH water) under LOW power.
2. DIAGRAM ONE cell and LABEL the following parts:
a. cell wall (rigid outermost boundary of the cell)
b. cell membrane (may be hard to see b/c may be flat against inside of cell wall)
c. chloroplasts (green ovals)
3. Switch to medium power and refocus .Then, switch to high power and refocus.
4. Observe the leaf on the left (in FRESH water) under HIGH power.
5. DIAGRAM ONE cell (on high power) and LABEL the following parts:
a. cell wall (rigid outermost boundary of the cell)
b. cell membrane (may be hard to see b/c may be flat against inside of cell wall)
c. chloroplasts (green ovals)
Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
Analysis Questions for Elodea in FRESH water:
Read/look at the following information before answering the questions (it will be
used to help you answer some questions):
 Elodea cell under normal isotonic conditions
(in fresh water):
1% salt
99% water
1% salt
99% water
1. For the cell under normal isotonic conditions (on LEFT side in FRESH water):
a. What is the percentage of water inside of the cell? __________________%
b. What is the percentage of water outside of the cell? _________________%
c. How do the percentages of WATER inside and outside of the cell compare?
(See # a & b.) _____(They are different. / They are the same.)_____
d. In this situation, what would the water do?
___(move into the cell / move out of the cell / show no net movement)___
i. Explain your reasoning in terms of osmosis (water movement).
_________________________________________________________
_________________________________________________________
e. Did the cell shrivel, stay the same, or swell? _______________________
What evidence do you have? _____________________________________
f. How were the chloroplasts arranged inside the cell?
_____(mostly near the center / along the edges)_____
Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
Observation of Elodea in SALT water Procedure:
1. Switch back to low power and move the slide so that you can OBSERVE the leaf
on the right (in SALT water) under LOW power.
2. DIAGRAM ONE cell and LABEL the following parts:
a. cell wall (rigid outermost boundary of the cell)
b. cell membrane (may be hard to see b/c may be flat against inside of cell wall)
c. chloroplasts (green ovals)
3. Switch to medium power and refocus .Then, switch to high power , refocus, and
OBSERVE the leaf on the right (in SALT water) under HIGH power.
4. DIAGRAM ONE cell (on high power) and LABEL the following parts:
a. cell wall (rigid outermost boundary of the cell)
b. cell membrane (may be hard to see b/c may be flat against inside of cell wall)
c. chloroplasts (green ovals)
Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
Analysis Questions for Elodea in SALT water:
Read/look at the following information before answering the questions (it will be
used to help you answer some questions):
 Elodea cell under hypertonic conditions
(in salt water):
~5% salt
~95% water
1% salt
99% water
1. For the cell under hypertonic conditions (on RIGHT side in SALT water):
a. What is the percentage of water inside of the cell? __________________%
b. What is the percentage of water outside of the cell? _________________%
c. How do the percentages of WATER inside and outside of the cell compare?
(See # a & b.) _____(They are different. / They are the same.)_____
d. In this situation, what would the water do?
___(move into the cell / move out of the cell / show no net movement)___
i. Explain your reasoning in terms of osmosis (water movement).
_________________________________________________________
_________________________________________________________
e. Did the cell shrivel, stay the same, or swell? _______________________
What evidence do you have? _____________________________________
f. How were the chloroplasts arranged inside the cell?
_____(mostly near the center / along the edges)_____
Name___________________________
Date _________
Mrs. Geithner-Marron (Bio 200)
Period ________
"Normal & Plasmolyzed Cells” Microscope Lab (Cells in Fresh & Salt Water)
General Analysis Questions:
1. Define “plasmolysis”. _____________________________________________
_____________________________________________________________
a. Did either cell show evidence of plasmolysis? _____(no / yes)_____
i. If so, which one? ___(the cell in fresh water / the cell in salt water)__
1. How can you tell? _____(the cell shriveled / the cell swelled up)_____
2. What causes osmosis (water to move across a cell’s membrane)?
_( different concentrations inside & out / equal concentrations inside & out)_
a. When osmosis occurs, water moves from ___(high to low / low to high)___
concentration.