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CELL LAB
CELLS
The cell is the basic unit of life. Some cells are visible to the naked eye, but most are microscopic. They range
from 0.1 µm (micron) to several ml (millimeters) in diameter. A micron is equal to one millionth of a meter in
length, so you can see that some cells are very tiny. A typical cell has a nucleus embedded in a jelly-like
cytoplasm. The cytoplasm is surrounded by a cell membrane. In plant cells, the membrane also is surrounded by
a cell wall.
OBSERVATION OF CORK CELLS
Introduction
During the first part of this laboratory, you will retrace Robert Hooke’s original experiment with cork cells.
Robert Hooke was the first scientist to recognize these building blocks of life and give them the name “cells.”
More than three hundred years have passed since Hooke first described cork cells in his book Micrographia.
Procedures
1. Obtain a prepared slide of cork. Examine the specimen under low, medium, and high power. On the data
page, draw what you can see. Use either 100X or 400X magnification. Label the cell wall.
2. Answer the analysis questions regarding the cork examination.
OBSERVATION OF ELODEA CELLS
1.
Prepare a wet mount of an Elodea leaf. A whole leaf obtained near the growing tip of the plant should be
used. Examine the leaf under low power of your microscope. Find a field of view in which the cells are
particularly distinct. Center this area in your microscope field, and bring it into focus under high power.
Use the fine adjustment knob to observe the cells at different depths.
2. Observe and identify the following: the cell wall, the nucleus, the central vacuole, and chloroplasts. The
nucleus probably is best seen as a circular lump near the cell wall. The vacuole is a large clear area
dominating the center of the cell. Chloroplasts are another type of plastid which appear as small, round,
green bodies in the cytoplasm. If you do not see movement among the chloroplasts at first wait a few
minutes and observe the cells again.
3. On the data sheet, draw a few Elodea cells. Use arrows to indicate chloroplast movement. Label your
drawing, indicating the cell wall, vacuole, chloroplasts, and cytoplasm.
4. Answer the analysis questions regarding the Elodea cells.
OBSERVATION OF A HUMAN CHEEK CELL (ANIMAL CELL)
1.
Gently scrape the inside surface of your cheek with a clean, flat toothpick. Do not hurt yourself. The
slimy surface of the inside of your mouth has many cells which come off easily without digging into the
cheek itself. Prepare a wet mount of the material that you have scraped from your cheek. Add a drop of
methylene blue to the slide then a coverslip on top. Examine the cells under low power. Switch to high
power and observe again.
2. Some stains, such as iodine solution, kills cells rapid once they come in contact with the cell. Other
stains, called vital stains, kill cells slowly. Vital stains, such as methylene blue, may be used as aids in
studying living cells. Methylene blue is differently absorbed by the nucleus and also by tiny granules in
the cytoplasm. Animal cells stained with methylene blue should show an obvious blue nucleus and a
place blue cytoplasm.
3. Draw your cheek cell on the data sheet. Label the cell membrane, cytoplasm, and nucleus.
4. Answer the analysis questions about cheek cells.
ANAYLSIS QUESTIONS
CORK CELLS
1.
Are all the cells of similar shape and size? Explain.
2. Are the cells filled with any material? Explain.
3. Are these cells alive? Explain.
ELODEA CELLS
1.
Are all the chloroplasts moving in the same direction?
2. Are all the chloroplasts moving at the same speed?
3. Can you observe anything which makes them move?
4. Explain how the chloroplasts move. Why does waiting a few minutes with the slide mounted in your
microscope increase the probability of chloroplast movement?
HUMAN CHEEK CELL
1.
How does the outer edge of a cheek cell compare with that of an Elodea leaf?
2. Describe the shape of your cheek cells. Are they all the same shape?
3. In what ways do cheek cells differ from Elodea cells?
4. Why did you use methylene blue in this experiment?
DATA SHEET
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CELL QUIZ
_____ 1. The green pigmented structures found in most plant cells are
a. chromophyll
b. chlorophyll
c. leucoplasts
d. chloroplasts
b. bacterial cells c. Elodea cells
d. animal cells
____ 2. Cell walls are not found in
a. plant cells
____ 3. Cytoplasmic steaming (movement) occurs in
a. Elodea cells
b. potato cells
c. cheek cells
d. blood cells
____ 4. A micron is
a. one hundredth of a meter
b. a ten thousandth of a meter
c. one thousandth of a meter
d. one millionth of a meter
____ 5. The stain which causes certain plant nuclei to turn a dark or light blue in color is
a. methylene blue b. iodine
c. ninhydrin
d. Benedict’s solution
____ 6. Methylene blue dye was used to stain the
a. onion cell
b. cheek cell
c. Elodea cell
d. potato cell
c. cell
d. electron
____ 7. The basic unit of life is the
a. organelle
b. virus
____ 8. Robert Hooke is credited with the discovery of the
a. nucleus
b. cell
c. cytoplasm
d. ribosome
____ 9. Student A observed a cell under the microscope. He identifies it as a plant cell and not an animal cell
Because he noted the presence of
a. a nucleus
b. a cell wall
c. ribosomes
d. a cell membrane
____10. Most cells lacking a cell wall would also lack a
a. mitochondria
b. chloroplast
c. vacuole
d. cell membrane