Lab: OBSERVING PLANT AND
ANIMAL CELLS
NAME:_____________________________
DATE:______________PERIOD:_______
PURPOSE: 1. To observe the differences between plant and animal cells using the light microscope.
2. To observe the effects of salt solution on Elodea cells.
BACKGROUND INFORMATION: The cell is the basic unit of structure and function in all living things. All of the
processes necessary for life occur in cells. In single-celled organisms, such as amoebas, all of the functions required by the
organism take place within one cell. Multicellular organisms, such as humans and plants, are made up of many cells with
different structures and functions. The shape and size of a cell, as well as the structures found inside it, are determined by the
functions of the cell.
When a plant cell is placed in a hypotonic solution, water molecules enter the cell, causing it to swell. But the cell does not burst.
Instead, the cell wall resists the osmotic pressure. Osmotic pressure within a plant cell is called turgor pressure. Turgor
pressure gives the soft tissues of plant stems and leaves their firm, rigid form. You have probably observed turgor in a crisp head
of lettuce. Plant cells that are swollen with water are said to be turgid. In a hypertonic solution, water molecules will leave the
cells of the plant. This causes the turgor pressure to drop. This loss of turgor pressure is called plasmolysis. Plasmolysis causes
plants to wilt.
MATERIALS: microscope, glass slide, coverslip, toothpick, Methylene blue (dye), Elodea leaf, salt solution, color
pencils (REQUIRED for all microscope drawings)
PROCEDURE:
PART I – ANIMAL CELL
1. Prepare a wet mount slide of a human epithelial cell by gently scraping the inside of your cheek with a clean toothpick.
Stir the toothpick in a drop of water on a glass slide. Add a small drop of Methylene Blue dye and a cover slip.
2. Examine the slide under both low (100X) and high (400X) power.
3. Draw and color what you observe in the viewing field under high power.
4. Label the cell membrane, cytoplasm, and nucleus of a single cheek cell. Label the magnification of the drawing.
5. Wash your hands with soap and water when completed.
PART II – ELODEA PLANT CELL
1.
2.
3.
4.
Prepare a wet mount slide of a single Elodea leaflet by placing the leaf on a glass slide in a drop of water.
Add a cover slip.
Examine the slide under both low (100X) and high (400X) power.
(NOTE: You may observe cytoplasmic streaming as the chloroplasts become warm on the microscope stage.)
Draw and color what you observe in the viewing field under high power.
Label the cell wall, chloroplast, and the central vacuole. Label the magnification of the drawing.
PART III – ELODEA PLANT CELL IN SALT SOLUTION
1. Using the Elodea slide prepared in Part II, place a drop of salt solution on the slide near one side of the coverslip.
Place a piece of paper towel on the opposite side of the coverslip to draw out the fresh water and pull the salt water
underneath the coverslip. (See diagram below.)
2. Observe the cell for a few minutes on high power (400X), then draw and color what you observe in the space provided.
RESULTS:
Human Epithelial Cell
Elodea Plant Cell in Fresh Water
___________X
__________X
Elodea Plant Cell in Salt Water
Draw and color a chloroplast. Label: chloroplast,
thylakoids, grana, stroma (See p. 208, P-H Biology)
__________X
ANALYSIS QUESTIONS:
1. Name two structures you observe in the plant cells that you do not observe in the animal cells?
1.)___________________________________
2.)___________________________________
2. Plants are stiff and immobile. What cellular structure is responsible for this characteristic? __________________
3. Explain why animal cells so much more variable in their appearance than plant cells? _______________________
___________________________________________________________________________________________
4. Explain the difference between the cell wall and the cell membrane.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
5. Explain what happened to the Elodea cells when they were exposed to the salt solution. (Include the terms:
hypertonic, osmosis, turgor pressure, and plasmolysis in your answer.)
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
6. Explain what effect, if any, the salt solution would have on the animal cell.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________