Name .........................................Date ...................... Cell laboratory #1
Over 300 years ago, Robert Hooke, an English scientist, described the appearance of cork under the microscope. He named the tiny, box-like structures he observed: cells. Cork, which does not contain living tissue, comes from the outer bark of the cork oak tree.
By the early part of the 19th century, it was accepted that all living things are composed of cells. Cells come in a variety of shapes and sizes, and they perform different functions. Although cells are different, they resemble one another because they share certain common structures. The microscope reveals that most plant cells and animal cells have various components including the nucleus, nucleolus, mitochondria, cytoplasm, and cell membrane.
Microscope Slides Cover Slips Razor
Medicine Dropper Water Cork Onion
Toothpick Forceps Iodine Paper Towels
Place the cork on several sheets of paper. Hold it firmly there. Using the razor, slice a very thin section (CAREFULLY CUT AWAY FROM YOURSELF).
Prepare a wet mount with this section and look at it under the low power of the microscope. Once focused, you may switch to the higher power. Now draw a picture of what you see and label the cell wall.
Describe the general shape of the cork cells.
What structures do you see inside the cell walls? Explain.
Cut into an onion and remove a thin section of the inner layer with the forceps. Prepare a wet mount with it. Observe it under the low power. Once focused, you may switch to high power. What shape are the cells?
Draw and label what you see.
What structures do you see that tells you that this is a plant cell?
Every plant cell is surrounded by a non-living cell wall composed chiefly of cellulose. Pressed tightly against the cell wall is the cell membrane, which surrounds the granular cytoplasm. The central part of the cell consists of the large, fluid-filled vacuole. The spherical nucleus appears as a dense body in the cytoplasm near the cell wall. It is surrounded by a nuclear membrane. Within the nucleus are nucleoli. Stain will help you see some of these structures in more detail, so add a drop of iodine solution to one side of the cover slip. Suck it to the other side using a piece of paper towel. (CAUTION: STAIN WILL STAIN !!!)
How many nuclei are present in each cell?
Draw what you see.
How does the cytoplasm in the stained cell differ from that of the unstained?
Use a toothpick to gently scrape some cells off the interior lining of your cheek. Prepare a wet mount of this. View it under the microscope and draw what you see.
How does it differ from plant cells? Why?
You may stain it if you choose.
Answer the following questions:
1. How can you tell that cork cells are nonliving?
2. When Robert Hooke examined cork cells, what did he really see?
3. Explain why cork floats on water.
4. What structures did you see in onion cells that you did not see in cork?
What structures did you see in both?