Download Observing Cells - GoldenBearScience7A

Name: _____________________________________
Date: _________
Per: ______
Observing Cells Lab
How do we know that all living things are made of cells?
Pre-Lab Questions
Read through the entire lab and then use the lab and your notes or textbook to answer the following
questions. You must have the pre-lab completed before you will be allowed to start the
lab. (1 point each)
1.
What stain, if any, will you use to look at Elodea cells under the microscope? __________________
2. What stain, if any, will you use to look at onion cells under the microscope? ___________________
3. What stain, if any, will you use to look at cheek cells under the microscope? __________________
4. How should you place the Elodea leaf on the slide? ______________________________________
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5. What will you use to scrape the inside of your cheek to obtain cheek cells? ___________________
6. What power will you use to draw sketches of the Elodea cell? ______________________________
7. What power will you use to draw sketches of the onion cell? _______________________________
8. What power will you use to draw sketches of the cheek cell? _______________________________
9. State the question that this lab is trying to answer: ________________________________________
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1.
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Observing Cells
Problem (Question): How do plant and animal cells differ?
Materials:
microscope
microscope slides
cover slips
forceps
dropper
water
flat toothpick
methylene blue stain
Iodine solution
Elodea leaf
onion peeling
Procedure:
Part I: Elodea Cells
1. Remove a young leaf from the tip of an Elodea plant. Place the leaf so that the under side of
the leaf is facing up when positioned on the slide. Add a drop of water and a cover slip.
2. Place the slide on the microscope stage.
3. Observe the leaf under low power. Slowly turn the fine adjustment of the microscope to see if
there is more than one cell layer in the leaf.
4. Next turn to medium power. Use the course adjustment knob, then the fine adjustment knob
to focus the specimen.
5. Turn to high power. Carefully focus on one cell. Look for any sign of movement in the cell.
6. Write your observations on the data table.
7. Draw the Elodea cell in the first space provided on your Sketch Page and label all parts.
8. Wipe your slide clean and throw away the small piece of Elodea.
Part II: Onion Cells
1. Remove a thin peel of onion and place on the center of a slide. (I will show you how to do this)
2. Put a drop of Iodine solution on the onion, then place the cover slip on top of the onion peel
and drop of iodine.
CAUTION: Iodine can stain skin or clothing. Rinse spills with plenty of water.
3. Observe under low power then carefully switch to medium power and focus.
4. Write your observations in the data table.
5. Draw the onion cells in the space provided on your Sketch Page and label all parts.
6. Wipe your slide clean, taking care not to get any of the Iodine solution on your hands or
clothing.
Part III: Cheek Cells
1. Put a drop of Methylene blue solution on the slide. CAUTION: Methylene blue solution can
stain skin or clothing. Rinse spills with plenty of water.
2. Gently scrape the inside of your cheek with the blunt end of a toothpick. CAUTION: Scrape
lightly. Cells will rub off on the toothpick but you will not be able to see them.
3. Stir the end of the toothpick in the stain. Then throw the toothpick away. CAUTION: Do
not reuse toothpick or leave the toothpick lying around.
4. Place a cover slip on the slide on top of the methylene blue drop (now with cheek cells in it!).
5. Observe the cells under low power and focus. Next switch to medium power and focus.
Finally, switch to high power and focus.
6. Write your observations in the data table.
7. Draw a cheek cell in the space provided on your Sketch Page and label the parts.
8. Remove cover slip and drop slide and cover slip into the container of bleach.
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Observing Cells: Data Table (1 point each)
Specimen: __________________________________
Type of Stain: _______________________________
Observations: ______________________________________________
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Total Magnification Power for sketch: _______________________
Field of View Diameter for power listed above: __________ mm
Estimated number of cells that fit across the FOV: __________
Estimated length of one cell (show work!):
= ________mm
Specimen: __________________________________
Type of Stain: _______________________________
Observations: ______________________________________________
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Total Magnification Power for sketch: _______________________
Field of View Diameter for power listed above: __________ mm
Estimated number of cells that fit across the FOV: __________
Estimated length of one cell (show work!):
= ________mm
Specimen: __________________________________
Type of Stain: _______________________________
Observations: ______________________________________________
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Total Magnification Power for sketch: _______________________
Field of View Diameter for power listed above: __________ mm
Estimated number of cells that fit across the FOV: __________
Estimated length of one cell (show work!):
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= ________mm
Analysis: Please answer the following questions using complete sentences. (2 points each)
1.
What organelles of the Elodea cell could you actually see?
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2. Compare and contrast the shape of the onion cell to the shape of the Elodea cell.
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3. What organelle is seen in Elodea and not in onion cells or cheek cells?
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4. Why do you not find the organelle identified in number 3 in onion cells?
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5. Why do you not find the organelle identified in number 3 in cheek cells?
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6. What organelles of the cheek cell could you actually see?
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7. What cell structure determines or defines the shape of a plant cell?
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Conclusion and Application Question:
Please answer the following questions using complete sentences. (6 points)
8. Based on your observations of the different cells, come to a conclusion about the differences
between the organisms the cells come from. You must include a discussion on the chloroplast
and the cell wall. This answer needs to be 3 to 5 sentences in order to be complete. (Hints: Why
do plant cells have chloroplasts and cells walls, while animal cells do not? What is different about
the way plants and animals obtain their food?)
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