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HONORS BIOLOGY
LAB: CELL PARTS
Background Information:
In this lab you will observe organelles found in certain plant and animal cells. Just as animals are made
up of smaller parts called organs (heart, lungs, liver, etc.), cells are made up of smaller parts called
organelles. If we wanted to observe the organs in an animal, it would be possible to dissect the animal
and look at all the organs. The cell is too small for us to dissect with our equipment but we can observe
several types of organelles by looking at different kinds of cells. We will look at four different kinds of
cells: onion, elodea, potato, and cheek. The organelles which we should be able to observe with our
microscopes are: cell walls, cell membranes, cytoplasm, food vacuoles and nuclei.
**Remember to use low power FIRST, and then move to medium and high power for optimum
magnification.
Procedures
Part A: ONION
In an onion bulb cell we can observe the nucleus, cell wall, and cytoplasm (cell contents).
1. Remove the almost transparent layer of cells from the inside of an onion bulb scale by lightly
digging into the scale with your fingernail.
2. Place this layer onto a microscope slide.
3. Add a drop of iodine to the slide.
4. Uncurl or unfold any overlapped portion of the cell layer. Make sure the layer is perfectly flat.
Add a cover slip.
5. Observe the cells under low, medium, and high power of your microscope. Note the "brick wall"
appearance of the cells with cell walls separating the cells.
6. Now locate a small round brown structure within the cell called the nucleus.
7. In your high powered drawing, label the nucleus, cytoplasm, and cell wall.
Part B: ELODEA:
In cells from an elodea leaf, we can observe Chloroplasts which are responsible for photosynthesis.
1. Prepare a wet mount slide using one elodea leaflet from the tip of the elodea plant.
2. Draw what this cell looks like under low, medium and high power.
3. Note the small green organelles inside each cell. These are the chloroplasts. Movement of the
chloroplasts within the cell can often be observed. Label the cell wall and chloroplasts.
Part C: POTATO
Food vacuoles that serve as food storage areas are visible in potato cells.
1. Obtain a piece of potato.
2. Use tap water to prepare a wet mount of the slice.
3. Add two drops of iodine.
4. Observe the cells under low, medium, and high power of your microscope.
Part D: HUMAN CELLS
Human cheek cells are used for protection. These cells are excellent for examining the cell membrane
(the outer covering), cytoplasm, and the nucleus.
1. Place a drop of iodine on a slide.
2. Gently scrape the inside of your cheek with the end of a toothpick.
3. Dip the toothpick into the iodine on the slide and mix once or twice. Throw the toothpick in the
wastebasket.
4. Add a cover slip to the slide; examine the material under low, medium, and high power of your
microscope. The cells will be very hard to see because they are almost transparent. Adjusting the
microscope diaphragm may help. Locate and examine cells that are separated from one another
rather than those that are in clumps.
5. Label the cell membrane, nucleus, and cytoplasm.
Data Table:
Low (x______)
Medium (x______)
High (x______)
Onion
Elodea
Potato
Cheek
Clean up: Onion skin, potato chunks, and toothpicks go in the waste paper basket. Rinse and dry your
slides and cover slips. Make sure the iodine bottle is closed. Return all materials to your cleaned and dry
lab tray. Unplug your microscope and wind the cord appropriately.
Analysis: (These should be answered using only complete sentences in your lab report).
1. What instrument did you use to see cells? Why?
2. Why are cells so small? (Look at your cell theory notes!)
3. Describe the shape of the onion skin, potato, and cheek cells. How are they similar and how are
they different?
4. What cell parts were you able to see in each type of cell?
5. Why is the nucleus not visible in the potato cell?
6. What is the purpose of the vacuole?
7. What name is given to the outer covering of a cheek cell? What is its purpose?
8. Cheek cells are flat like pancakes. How might the shape of cheek cells relate to their function?
(Compare the shingles on a roof to cheek cells in your mouth)
Conclusion: Use the directions in your lab prep to help you write a well-though out, detailed conclusion.