Plant & Animal Cell Structure Observations
A wet mount slide includes the following: a slide, a cover slip, a specimen, a drop of stain or water. When preparing a slide, hold the cover slip at an angle and let it drop onto the slide slowly trapping the specimen between the two pieces of glass. A piece of celery skin is easy to use in this first activity.
SPECIMEN 1: Onion Membranes
a. First take a thin layer of onion or celery skin off the onion or celery.
b. Put it flat on a slide.
c. Put a drop of iodine stain on it.
d. Carefully put on a cover slip remembering to angle it.
e. Examine the cells under low, then medium power, and then carefully move the objective lens to high power.
f. Draw a few cells showing what you observed on high power.
SPECIMEN 2: Cheek Cells
a. Using a toothpick scrape the inside of your mouth.
b. Place it carefully on the center of the slide.
c. Place a drop of methylene blue stain on it.
d. Repeat steps d-f from the onion or celery skin directions.
Label the following structures if present on your drawings. Use a ruler for all lines to your labels:
- Cell Walls: Plants have thick cell walls to strengthen the plant stem.
- Cell Membranes: Animals have thin membranes because they have other forms of skeletons. Plants have cell membranes just underneath their cell walls.
- Chloroplasts: Plants have green colored structures that produce food by photosynthesis.
- Nucleus: Both plants and animals have these; they control heredity and cell division.
- Cytoplasm: Both plants & animals have clear liquid/gel where most of the cell's life functions occur.
Answer the following questions from your observations:
1. Describe the general shape of onion or celery epidermal cells.
2. How can you tell that these cells have thickness (depth) using the microscope?
3. Which parts of the onion or celery cells became more visible after staining?
4. In which way were the cheek cells similar to the onion skin cells? How did they differ?
5. What are the functions of the cell wall?
6. Since the plant cell has a cell wall and a cell membrane, what is the advantage to the plant over just a cell membrane? What are the disadvantages?