The Cell

1. List the 3 parts of the Cell Theory

Materials needed: microscope, two glass slides, iodine stain (Lugol's solution),

methylene blue stain, two cover slips, an onion, and a toothpick

PART A: Plant Cells (Onion Skin Wet Mount)

1. Peel the delicate transparent tissue from the inner surface of a piece of onion using forceps (tweezers).

2. Make a wet mount by placing the tissue, unwrinkled, in a small drop of water on a glass slide.

3. Add one small drop of Lugol's iodine stain to the tissue and cover with a cover slip as directed. (* be careful - the Lugol's can stain and burn the skin!)

4. Examine the onion cells at low power, focus as necessary.

5. Next examine the cells at medium and high power.

6. Prepare a diagram of onion skin tissue showing three to four cells. Label the structures you can identify from the microscope. (examples - cell membrane, nucleus, etc.) Remember to follow guidelines for drawing and labeling a proper biological diagram.

Draw four onion cells in your lab book

Answer the following questions: Write both the question and answer in your lab book

1. Describe the shape of the cells. ______

2. What cell structures and organelles can you see? ______

3. Why are no chloroplasts evident? ______

Part B- Elodea cells

1. Obtain one leaf and make a wet mount slide.

4. Examine the Elodea cells at low power, focus as necessary.

5. Next examine the cells at medium and high power.

6. Prepare a diagram of your leaf showing three to four cells. Label the structures you can identify from the microscope. (examples - cell membrane, nucleus, etc.) Remember to follow guidelines for drawing and labeling a proper biological diagram.

Draw four Elodea cells in your lab book

Answer the following questions: Write both the question and answer in your lab book

1. Describe the shape of the cells. ______

2. What cell structures and organelles can you see? ______

3. Why didn’t you need to stain the Elodea cells? ______

3. Why were chloroplasts evident? ______

PART TWO: Cheek cell wet mount

1. To view cheek cells, gently scrape the inside lining of your cheek with a toothpick. DO NOT GOUGE THE INSIDE OF YOUR CHEEK! (We will observe blood cells in a future lab!! )

2. Gently tap the toothpick onto the center of a glass slide. Some of the cheek cells should

fall onto the slide.

3. Add a drop of methylene blue stain (specific for animals) and cover with a cover slip.

4. Observe the cheek cells under both low and high power of your microscope. Draw a diagram of one cheek cell, using a pencil, and label its parts. (At minimum you should observe the cell membrane, nucleus, and cytoplasm.)

Draw your cheek cell in your lab book

Conclusion: To be answered in your lab bookWrite both the question and answer in your lab book

II. Why do we stain specimens?

III. Why must the specimen you observe be very thin?

IV. Onion cells are plants. Therefore, why were there no chloroplasts in the onion cells you observed?

V. Centrioles might be observed in some of these cells with an electron microscope. In which cells wouldthese be observed and what is the function of these cell organelles?

VI. What is the general shape of a typical plant cell? …of a typical animal cell?

VII. Inside the mouth, these cells are joined together in a sheet. Why are they scattered on your slide?