Download Plasmolyzed Cells Lab

Plasmolyzed Cells Lab
Name ___________________________________________
Background
Date ________________________
Diffusion of water molecules across a cell’s
Per ________
membrane from an area of high water concentration
to an area of low water concentration is called
Station _______
osmosis. This movement of water may be harmful
to cells. If too much water is lost from the cell, the
plasma membrane and the cell contents shrink. This is called plasmolysis. Plasmolysis may lead to death of
the cell. Most cells live in an environment where movement of water in and out of the cell is about equal.
Therefore, there are no harmful effects to the cell.
Materials
compound light microscope
coverslip
tap water
microscope slide
Elodea (water plant)
6% salt solution
paper towel
droppers (2)
forceps
Procedure
1. Prepare a wet mount of an Elodea leaf as follows. Use Figure 1 as a guide.
2. Use a dropper to place one or two drops of tap water on a microscope slide.
3. Place one Elodea leaf in the drop of water. Cover the leaf with a coverslip.
4. Observe the leaf under both low and high powers. Note the location of chloroplasts in relation to the cell
wall.
5. Diagram a normal cell in the Data section. Label the cell wall, plasma membrane, and chloroplasts.
6. Use a clean dropper to add a 6% salt solution along one edge of the coverslip. Place a piece of paper
towel along the opposite edge of the coverslip. The tap water will soak into the paper towel, drawing the
salt solution under the coverslip.
7. Allow the sample to remain in the 6% salt solution for 7 – 10 mins. While you wait, you can begin
answering the Analysis Questions.
8. Observe the leaf under both low and high powers. Again, note the location of the chloroplasts in relation to
the cell wall. If the plasma membrane and the cell contents have shrunk away from the cell wall, the cell
has plasmolyzed.
9. Diagram a plasmolyzed cell in the Data section. Label the cell wall, plasma membrane, and chloroplasts.
10. Add a drop of tap water to the wet mount, following the procedure in step 6. Observe the appearance of the
cells.
11. Clean your slide and coverslip in the sink with tap water. Dry all materials, and place back in your station
basket. Turn off your microscope.
Pre-Lab Questions (3 pts each, 15 pts total)
You do not need to write the question. You do NOT need to write in complete sentences. Use your notes from
Diffusion and Osmosis to answer the pre-lab questions.
1. Define osmosis.
2. Define passive transport.
3. Discuss the difference between simple and facilitated diffusion.
4. Define plasmolysis.
5. What happens to a cell that has been plasmolyzed?
Data (35 pts)
Don’t forget to label the cell wall, plasma membrane, and chloroplasts.
Normal Plant Cell
Plasmolyzed Plant Cell
Magnification: _____X
Magnification: _____X
Analysis Questions (4 pts each, 40 pts total)
For Questions 1-5, write the word(s) that best complete(s) the sentence.
In each diagram below, a “cell” with a semipermeable membrane has been placed in a beaker containing substances that
are dissolved in water. The membrane is permeable to water. It is not permeable to glucose or starch.
1.
a. The cell is __________________________ to its surroundings.
b. The environment is __________________________ to the cell.
20% glucose
10% glucose
c. Water will travel (into/out of) the cell. [If isotonic, write “Equilibrium”.]
d. The cell will (shrink/swell/remain the same).
2.
a. The cell is __________________________ to its surroundings.
7% starch
7% starch
b. The environment is __________________________ to the cell.
c. Water will travel (into/out of) the cell. [If isotonic, write “Equilibrium”.]
d. The cell will (shrink/swell/remain the same).
3.
a. The cell is __________________________ to its surroundings.
b. The environment is __________________________ to the cell.
c. Water will travel (into/out of) the cell. [If isotonic, write “Equilibrium”.]
25% starch
4% starch
d. The cell will (shrink/swell/remain the same).
4.
3% glucose
a. The cell is __________________________ to its surroundings.
b. The environment is __________________________ to the cell.
12% glucose
c. Water will travel (into/out of) the cell. [If isotonic, write “Equilibrium”.]
d. The cell will (shrink/swell/remain the same).
5.
a. The cell is __________________________ to its surroundings.
b. The environment is __________________________ to the cell.
c. Water will travel (into/out of) the cell. [If isotonic, write “Equilibrium”.]
4% starch
4% glucose
d. The cell will (shrink/swell/remain the same).
Answer the following questions below. You do not need to write in complete sentences.
6. Describe the location of the chloroplasts in a normal plant cell (in tap water).
7. Describe the location of the chloroplasts in a plasmolyzed plant cell (in salt solution).
8.
a. How did the cells change when salt water was added to the wet mount?
b. In which direction did water move through the plasma membrane of the cells when salt solution
was added?
9.
a. How did the cells change when tap water diluted the salt solution?
b. In which direction did water move through the plasma membrane when tap water diluted the salt
solution?
10. What is the term used to describe when too much water is lost from the cell, causing the plasma
membrane and the cell contents shrink?