Download Human Skin cells

Comparing Cells Lab
Today
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we will view three different types of cells under the microscope:
Onion skin cells (prepared slide)
Green Leaf cells (you will make)
Human skin cells (you will make)
Onion skin cells
1. Collect an onion root tip slide from the cart.
2. Make sure the lowest power lens (the shortest lens) is in place over the stage and the
microscope light is turned on. Place the slide onto the stage of the microscope.
3. Look through the eyepiece and turn the coarse adjustment knob (the largest knob) until
an image comes into focus. It should look like a brick wall or like lizard skin.
4. On your lab worksheet, draw a picture of what you see in the circle labeled 40x. Label
as many parts of the cell as you can see.
5. Looking from the SIDE of the microscope, rotate the lenses to the medium powered
objective lens (10x). If you need to, use the fine focus knob (the smallest knob) to get
the image into focus—DO NOT MOVE THE COARSE ADJ KNOB. You should see a dark
blob in the middle of each cell.
6. On your lab worksheet, draw what you see in the 100x circle. Label as many parts of the
cell as you can see.
7. Looking from the SIDE of the microscope, rotate the lenses to the highest powered
objective lens (40x). If you need to, use the fine focus knob (the smallest knob) to get
the image into focus—DO NOT MOVE THE COARSE ADJ KNOB.
8. On your lab worksheet, draw what you see in the 400x circle. Label as many parts of the
cell as you can see.
9. Rotate to the lowest power lens and THEN remove the slide. Return the slide to the cart.
Green leaf
1. Using the forceps, tear off one small leaf from the elodea plants floating in the beaker.
2. Add one drop of water from the beaker to the slide.
3. Stand a thin glass cover slip on its edge near the leaf, next to the drop of water.
4. Slowly lower the other side of the cover slip until it covers the leaf completely. Make
sure there are no air bubbles.
5. Make sure the lowest power lens (the shortest lens) is in place over the stage. Place the
slide onto the stage of the microscope.
6. Look through the eyepiece and turn the coarse adjustment knob (the largest knob) until
an image comes into focus. It should look like small green bricks or like lizard skin.
7. On your lab worksheet, draw a picture of what you see in the circle labeled 40x. Label
as many parts of the cell as you can see.
8. Looking from the SIDE of the microscope, rotate the lenses to the 400x lens. If you
need to, use the fine adjustment knob (the smallest knob) to get the image into focus.
The little green dots should get larger.
9. On your lab worksheet, draw a picture of what you see in the circle labeled 100x. Label
as many parts of the cell as you can see.
10. Looking from the SIDE of the microscope, rotate the lenses to the highest powered
objective lens (40x). If you need to, use the fine focus knob (the smallest knob) to get
the image into focus—DO NOT MOVE THE COARSE ADJ KNOB.
11. On your lab worksheet, draw what you see in the 400x circle. Label as many parts of the
cell as you can see.
12. Rotate to the lowest power lens and THEN remove the slide. Wipe the slide with a dry
paper towel and use the slide and coverslip for the next part.
Human Skin cells
1. One person in your group needs to wash the underside of their wrist with soap and
water. Dry thoroughly with a paper towel.
2. Stick a clean piece of clear tape on the underside of the washed wrist.
3. Gently remove the tape from the wrist being careful to avoid getting fingerprints on the
tape. You may use a forceps to do this.
4. Place the tape, sticky side up, on a clean microscope slide.
5. Stain the top, sticky side of the tape with 1-2 drops of methylene blue solution. Be
careful, this stain will permanently stain your clothing.
6. Use a forceps to carefully place a cover slip over the stained, sticky tape. Lower the
cover slip down onto the tape and then remove the forceps.
7. Make sure the lowest power lens (the shortest lens) is in place over the stage. Place the
slide onto the stage of the microscope.
8. Look through the eyepiece and turn the coarse adjustment knob (the largest knob) until
an image comes into focus. It should look like scattered blobs. Move the slide around
until a nice cluster of blobs moves into the center of your image.
9. Use the fine focus knob (the smallest knob) to make the image as focused as possible.
10. On your lab worksheet, draw a picture of what you see in the circle labeled 40x. Label
as many parts of the cell as you can see.
11. Looking from the SIDE of the microscope, rotate the lenses to the 400x lens. If you
need to, use the fine adjustment knob (the smallest knob) to get the image into focus.
12. On your lab worksheet, draw a picture of what you see in the circle labeled 100x. Label
as many parts of the cell as you can see.
13. Looking from the SIDE of the microscope, rotate the lenses to the highest powered
objective lens (40x). If you need to, use the fine focus knob (the smallest knob) to get
the image into focus—DO NOT MOVE THE COARSE ADJ KNOB.
14. On your lab worksheet, draw what you see in the 400x circle. Label as many parts of the
cell as you can see.
15. Rotate to the lowest power lens and THEN remove the slide. Place the used slide in the
beaker (on the cart) labeled USED SKIN CELL SLIDES.
Return to your seats to answer the lab follow-up questions on the remainder of your
answer sheet.
Conclusion questions
Answer the following questions in your lab notebook. Use your pictures to answer the questions
but feel free to look at your slides again if you need to remind yourself what you saw.
1. Why do we need to stain some of the cells with a dye like iodine or methylene blue?
What color do you think the cells would be without the dye?
2. What does “100x” magnification mean?
3. List the parts of a cell you could see in the cheek cells at 40x magnification.
4. List the parts of a cell you could see in the cheek cells at 400x magnification.
5. What might you be able to see at 4000x magnification that you couldn’t see with these
microscopes?
6. Describe the shape of the plant cells. Describe the shape of the animal cells. What
makes them different?
7. The onion skin cells and the elodea leaf cells are both plant cells but only one had
chloroplasts and chlorophyll. Why?