Download Cell Observation Exercise - Mr. Hill`s Science Website

Cell Observation Exercise
Materials
Compound microscope
Yogurt
Forceps
Methylene blue
Paper towel
Ruler (clear)
Anacharis leaf
Geranium leaf
Three slides (blank)
Iodine stain
Onion
Pipette
Coverslips
Cotton swab
Safety Concerns: Methylene blue & iodine. Methylene blue is
a corrosive and will burn. Do not get it on your skin. Iodine
is very toxic if swallowed or inhaled, can be absorbed through
the skin, and is a corrosive. Wash any area on your body that
is contaminated with either methylene blue or iodine
immediately with water. Inform Mr. Hill immediately. All
students will wear gloves and goggles while preparing slides.
Procedure
1. Take your clear ruler and place it on the microscope’s stage. Place the objective lens
on low power (40x). Look through the microscope and determine the diameter of the
field of view. Repeat this process for the field of view for the medium (100x) and high
power (400x) objectives. Record your information.
Part I – Prokaryotic Cell
1. Place a dab of yogurt on a microscope slide. Mix the yogurt in a drop of water, add a
coverslip, and examine it with a microscope.
2. First, focus the low-power objective (40x). Then, rotate to the medium-power (100x)
and focus. Finally, use the high-power objective (400x) to see masses of rod-shaped
cells. (If you can’t find the rod-shaped bacteria, prepare a new sample and, after mixing
it with water, place a drop of methylene blue to stain your sample.)
3. Complete Part I on the worksheet.
Part II – Plant Cells (Eukaryotic Cells)
1. Place a drop of water in the middle of a clean slide. Using the forceps, gently remove
a section of the skin from the inside layer of the onion and place it on the slide in the
drop of water.
2. Put the cover slip over the top by placing the edge of the cover slip on the end of the
drop of water. Then, gently lower the cover slip down on the drop of water.
3. Observe through the microscope (by first using low-power and working up to highpower). On your worksheet, draw what you see. Be sure to identify any organelles you
see.
4. Now, place one drop of iodine on the slide just to the side of the cover slip. Let the
slide set for 3 minutes letting the iodine stain the cells. Observe the cells through the
microscope. Do you see more details in the cell? On your worksheet then draw one cell in
that space, labeling all the parts identified. Include as many structures as you can see.
Indicate the power at which you are observing the cell and give the estimated size of
the cell (length and width). Clean and dry the slide and cover slip when done. Possible
structures that could be identified: cell wall, cell membrane, cytoplasm, nucleus,
nucleolus, mitochondria, vacuole.
5. Place a drop of water on the slide again, and put an anacharis leaf in the water. Put
the cover slip in place as you did before and observe the leaf through the microscope
(again going from the scanning objective to high-power).
6. Observe a cell. You may have to use a lower power to see all of one cell at a time. On
your worksheet, make a drawing of the cell and label all of the structures that you see.
Clean and dry the slide after your observations and data collection. Possible structures
that could be identified: cell wall, cell membrane, cytoplasm, nucleus, nucleolus,
mitochondria, vacuole, and chloroplasts.
6. Complete Part II on the worksheet.
Part III – Animal Cells (Eukaryotic Cells)
1. Place a drop of methylene blue in the middle of the slide. With a cotton swab, rub the
inside of your cheek, and then stir the cotton swab in the methylene blue.
2. Place a cover slip over the methylene blue as you have done before to avoid air
bubbles, and then place the slide under the microscope.
3. Observe starting with the low-power objective and working up to the high-power
objective. On your worksheet, make a drawing of the cell and label all of the structures
that you see. Clean and dry the slide after your observations and data collection.
Possible structures that could be identified: cell membrane, cytoplasm, nucleus,
nucleolus, mitochondria, vacuoles. Answer all the questions on the data sheet and turn in.
4. Complete Part III on your worksheet.
Part IV – Clean-up
Make sure that your work area is clean and that the microscope is not left on high
power, that it is unplugged and covered, that the slides have been cleaned and are dry
and the work area is ready for the next team.
Name ___________________________________________________________________
Cell Observation Exercise
Pre-Lab Questions – 25 points
Read the entire lab and answer the questions below. These questions must be answered
BEFORE you are allowed to do the lab.
1. What two types of plant cells are you observing? ________________________________
2. What precautions do you need to take when using the methylene blue stain? ____________
________________________________________________________________________
3. Why should you use forceps when obtaining the plant cells? ________________________
________________________________________________________________________
4. What is the purpose of the methylene blue stain in Part B of the lab? _________________
________________________________________________________________________
5. How do you remove the stain from underneath the coverslip (include the part and step where
you find it in the procedures)? ________________________________________________
________________________________________________________________________
6. Explain what you do with your slide when you are finished. _________________________
________________________________________________________________________
7. What magnification are you to use when you draw your observation of the cells? _________
_______________________________________________________________________
8. Is the methylene blue stain corrosive, alkaline, or neutral? _________________________
9. Explain how you clean-up your work area.
10. What do you use the clear plastic ruler to measure?
Name ______________________________________________ Score _________
Cell Observation Exercise
Make sure you label all your drawings.
Field-of-View Measurements
Low-power - ____________mm
Medium-power - ____________mm
High-power - ____________mm
Observations
Part I
Draw your observations below.
Type of cell _____________________________
Magnification (circle one)
Low
Medium
High
Part II
Draw your observations below.
Type of cell _____________________________
Magnification (circle one)
Low
Medium
High
Type of cell _____________________________
Magnification (circle one)
Low
Medium
High
Part III
Draw your observations below.
Type of cell _____________________________
Magnification (circle one)
Low
Medium
High
Analysis and Conclusions
1. What is the general shape of the plant cell? ______________________________
2. What is the general location of the nucleus in the plant cell?
3. What is the shape of the cheek cell? ___________________________________
4. What is the general location of the nucleus in the cheek cell?
5. Why are stains used when observing cells under the microscope?
6. Why is it possible to easily collect cells by gently scraping the inside of your cheek?
7. In general, the surface of a tree has a harder “feel” than does the surface of a dog.
What cell characteristic of each organism can be used to explain this difference?
(Hint – think about an organelle)
8. If you were given a slide containing living cell from an unknown organism, how would
you identify the cells as either plant or animal?
It is difficult to say what is impossible, for the dream of yesterday is
the hope of today and the reality of tomorrow.
-Robert Goddard