Download How Plant and Animal Cells Differ

How Plant and
Animal Cells Differ
DRAWINGS
Laboratory drawings can be made using several methods. Some
drawings are made in circles that represent the viewing field of a
microscope or another type of magnifier. When completing these
drawings, be sure to include the magnification at which you viewed
the object. Other laboratory drawings represent organisms or parts of
organisms. These drawings show the relative size, shape, and location
of anatomical structures. When completing representative drawings,
make the structures as clear and as accurate as possible.
Most laboratory drawings are labeled. Use the following
guidelines to help make your laboratory drawings.clear and legible:
•Use a ruler to draw label lines.
•Label lines should point to the center of the structure being labeled.
•Do not write on the label lines.
•Print all labels horizontally.
•Label the right-hand side of the drawing, if possible.
•Do not cross, label lines.
EXERCISE 3
The following drawing was made without using the guidelines above.
Circle those parts of the drawing that do not follow the guidelines.
Then, on the lines provided, explain how the drawing should be done.
Figure 2
AVERAGES
Occasionally you will be required to find the average of data gathered
from an investigation. To find an average, add the items in the group
together and then divide the total by the number of items. For
example, if there were five students of different ages—12,13,14,17,
and 19—how would you find the average age of the group? Add the
five ages together and divide the total by 5, which is the number of
items (students) in the group. What is the average age of this group of
students? Your answer should be 15 years old.
How Plant and
Animal Cells Differ
Background
Although plant and animal cells have many structures in common, •
they also have basic differences. Plant cells have a rigid cell wall, and il
they are green, they also have chloroplasts. Animal cells lack both a cell
wall and chloroplasts. They- also lack -the central uacuole common to
plant cells.
You will observe and compare animal cells and plant cells. You will
first examine epithelial cells from the inside of your cheek. Epithelium
is a type of tissue that covers the surfaces of many organs and cavities
of the body.
You will \\^o
ohirpr^ oni'or\ epidci'iMO.! cells . TK^^c
Ure. fhe layfs of •^^e oi|on.
Objectives
In this activity you will:
1.Observe human epithelial cells.
2.Observe onion cells.
3.Describe the differences between animal cells and plant cells.
Materials
microscope
forceps
slides
Lugol's iodine solution
in dropper bottle
methylene blue stain
in dropper bottle
cover slips
toothpick
pipette
oniol
water
Procedures and Observations III
PART I. HUMAN EP^THELIAL CELLS
1. Place a drop of water on a clean slide. Obtain epithelial cells by gen
tly scraping the inside of your cheek with a clean toothpick as
shown in Figure 1. CAUTION: Never reuse a toothpick or put any
thing in your mouth which may not be clean. Stir the material from
the toothpick in the drop of water on the slide. Then immediately
break the toothpick in half and throw it away.
Figure 1
2. Add a small drop of methylene blue stain to the slide. CAUTION:
Stain can damage clothing and discolor skin. Use a clean toothpick to
stir the cells on the slide, then immediately break the toothpick and
throw it away. Carefully place a cover slip on tKe slide. Examine the
slide under low power. When you find some cells that are separate
from each other, examine them under high power. Recall that you
may have to adjust the diaphragm to reduce the intensity of the
a. Make a^^rawing of two or three celb as they appear under high
power. Label the nucleus, nuclear membrane, cytoplasm, and cell
membrane of one of the cells,
(use
b. What is the shape of the cells?
c. Describe the appearance of the cytoplasm.
1.Cut an onion bulb into quarters.
2.-Take an inner layer of the onion and, with a razor blade, cut several
l/Z-cm squares through the paper-thin epidermis lining the leaf. Then,
with a forceps, remove one of the squares of epidermal tissue. Place
it in a drop of water on a slide. Add a cover slip. This procedure is
shown in Figure 2.
Figure 2
3. Examine the wet mount under low power. Adjust the light to provide
the best contrast,
a. What is the shape of the cells?
3. Explain that the cell mem
brane is immediately inside
the cell and is sometimes dif
ficult to see.
Every plant cell is surrounded by a nonliving 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 nucleolL
b. Make a diagram of a single cell. Label only the parts you see.
A (use
c What structure do you see that indicates these are plant cells?
4. Carefully focus on the cytoplasm near the cell wall.
d. Describe the appearance of die cytoplasm and any motion that you
observe.
Stain will enable you to see many cell structures In more detail.
5. Add a drop of Lugol's iodine solution to one side of the cover slip on
your onion slide. CAUTION: Stain can damage clothing and discolor
skin. Take a strip of paper towel and touch it to the water at the
opposite edge of the cover slip. See Figure 3. This should pull the
stain under the cover slip. If more stain is needed, repeat the proce
dure. Carefully observe the slide under low power, then high power.
e. How many nuclei art present in each cell?
f. What structures do you see in the nucleus? Now many are there in
each nucleus?
•Name.
Observing
Onion Cells (continued)
g. How does the cytoplasm in the stained celt differ in appearance
from the cytoplasm in the unstained cell?'
Remind studentsto add
water to the edge of the
cover slip if the specimen
dries out
a. plasma membrane
_Ab report
NAME.
Plant and
CLASS .
. DATE .
Animal Ceils
1. What structures are found in plant cells but not in animal cells?.
2. What is the purpose of staining the onion cells? .
3. Describe hew stain is applied to a slide holding a wet mount preparation..
4. Typical Plant and Animal Cells
Animal cel
Plant cell
5. Give the functions of the cell parts listed below,
b. cytosol.
c nucleus _
d. mitochondrion.
Laboratory Investigation 5A
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