CLASS COPY - do not write in booklet.
Complete all work on student handout
CELLS: The Basic Unit of Life
Objectives:
SWBAT observe a variety of living & once living cells using a light microscope
SWBAT study and locate specific cell parts including the cell wall, cell membrane,
cytoplasm, nucleus, and chloroplasts
SWBAT compare and contrast the cell parts found in animal and plant cells
NOTE: Lab Practical
During this lab your teacher will be grading EVERY individual on their ability to prepare a slide and bring
it into focus at high power & identify the parts of the microscope. Therefore, make sure you and your
partner both practice these skills.
PART I: Introduction to Microscopes
General Guidelines
1. When carrying a microscope, use both hands, one beneath the base and the other hand holding
the arm of the microscope
2. Place the microscope on the lab table at least 5 cm (2 in) from the edge of the table
3. Adjust the revolving nosepiece so that the lowest power objective is in line with the body. Make
sure it clicks into place or you won’t be able to see anything
4. You will view organisms on glass or plastic slides. The slides are either pre-prepared or you will
learn how to prepare them yourself. When using the slide, place it on the stage and secure it with
the clips. The slides are fragile and can be easily broken
5. The diaphragm regulates the amount of light coming through the stage. Making adjustments to
the diaphragm can be very helpful in allowing you to see your specimen. Experiment with different
light levels.
6. Starting with the stage lowered to the bottom, use the coarse adjustment to move the stage
upward until your slide is in focus. The use the fine focus to refine your view.
7. Make sure the image is in the center of your field of vision. Now move to medium, then finally to
high power. Do NOT lower the stage in between adjustments.
8. ONLY USE THE FINE FOCUS IN HIGH POWER!!!
9. When you have finished, removed, clean, and dry the slide and cover slip and return to materials
area. Unplug the microscope, wrap the cord around the scope and return to the cart.
10. Sometimes the lenses or eyepiece will need cleaning. Clean ONLY with lens paper specifically
designed for this purpose to avoid scratching the lens.
Identifying Parts:
Look over your microscope and identify the parts in the box. Use the diagram as a guide.
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Eyepiece. Eyepiece is 10X (magnifies images 10
times)
Objective lenses. These magnify 4X, 10X, and 40X
respectively. The longer the lens, the higher the
magnification.
Arm
Stage
Coarse focus knob & fine focus knobs (the position
of these varies based on microscope type)
Diaphragm
Light source
Base
On/off switch
Light source
Review Questions: Answer the following questions in complete sentences in your journal.
1. Explain how you should carry a microscope from one part of the room to another.
2. Explain why you should never use the coarse adjustment knob under high power.
3. When done using the microscope, describe what you should do before returning it to its proper
place.
4. What is the magnification of the eye piece?
5. What is the total magnification under:
a. Lower Power
b. Medium Power
c. High Power
NOTE: To calculate total magnification, multiply the eyepiece magnification by the objective lens
magnification.
PART II: Practice Viewing Specimens
The Letter ‘e’
Procedure1. Carefully cut out a small lower case ‘e’ from the newspaper. Place it on the center of a slide.
2. Place a drop of water on the newspaper cutout
3. Get a small coverslip and hold it by the edges. Place it on top of the newspaper cutout. Gently
lower the coverslip at an angle, this helps prevent air bubbles (see picture)
4. On your student handout sketch the letter as it appears on the slide. Label your sketch
“letter ‘e’ without microscope”
5. Using the low power objective, place the slide on the stage. Focus using coarse, then fine
adjustments. On your student handout, sketch it as it appears under low power only. Label
your picture “letter e under low power”
6. On your student handout, answer the corresponding questions:
7. Carefully rotate the objective lens to a higher power. Adjust using ONLY the fine focus now. On
your student handout, Sketch what you see.
PART III: Viewing Cells
Animal Cells: Human Cheek Cells
Methylene blue stain
Human Cheek cells provide a good view of the cell
membrane, nucleus and cytoplasm of an animal cell.
Procedure:
1. Place a drop of methylene blue stain onto the
center of the slide. CAUTION: the dye can stain
your skin and clothes.
2. Gently scrape the inside of your cheek with a
clean flat-edged toothpick.
3. Dip the toothpick into the stain on the slide and
mix gently twice.
4. Carefully add a cover slip at an angle to avoid
bubbles.
5. Throw toothpick in the garbage.
6. Under low power, locate and examine cells that
are separated from one another rather than
those in clumps.
7. Increase magnification to medium then high power.
8. On your student handout, make a detailed drawing of what you see. Label the cell
membrane, nucleus and cytoplasm.
9. Remove and clean slide. Replace microscope and all materials to their proper locations.
Plant Cells: Onions
Onion cells provide a view of a plant cell’s nucleus and cytoplasm.
Procedure
1. Use a fingernail to pull off a thin piece of tissue (1 cell
layer thick) from the inside section of an onion
2. Place the layer on a microscope slide and make sure it
lies flat on the slide
3. Add a drop or two of iodine stain to the onion layer.
NOTE: Iodine stains clothes and skin
4. Carefully place a cover slip on top of the onion layer,
making sure there are no bubbles.
5. First observe the cells under low power.
6. Locate the nucleus. The nucleus will appear as a small
round structure within each cell
7. Increase magnification to medium and high power. Can
you identify any other cell structures?
8. On your student handout, make a detailed drawing
of what you see. Label cell wall, nucleus, and
cytoplasm.
9. Remove and clean slide and coverslip. Throw onion cells in the garbage.
Plant Cells: Elodea
You will be viewing the cell wall and the green chloroplasts found in the cells of an Elodea water plant.
Procedure:
1. Retrieve one leaflet of the plant from the aquarium and place
it on the slide.
2. Add a few drops of water to prepare a wet mount
3. Using low power, position your slide along the edge of the leaf
margin. Locate the green, oblong cells.
4. Examine these cells under medium, then high power.
5. Find the small, green organelles inside each cell. These are
the chloroplasts.
6. On your student handout, make a detailed drawing of what
you see. Label the cell wall and chloroplasts.
7. Slowly move slide around to different parts of the elodea
leaf. See if you can locate movement
8. On your student handout, answer the questions
9. Remove and clean the slide. Throw the elodea leaflet in the garbage.
PART IV: End of Lab Questions
1. Propose an explanation for why plant cells have a cell wall and animal cells do not? (Hint: what is
the function of cell walls?)
2. Explain why animal cells do not have chloroplasts.
3. Propose an explanation for the fact that elodea cells have chloroplasts but onion cells did not.
4. Predict: all the cells we looked at were microscopic. Are all cells that small? Explain your answer!