Download Cell Lab Standard

Biology I Laboratory
CELLS: THE BASIC UNITS OF LIFE
Objectives:
NAME _________________
Block______
To recognize the differences in structure between plant and animal cells
To identify and observe cells through a compound light microscope
I. Procedures and Observations
A. Onion Cells
Peel the thin membrane from the inner (concave) side of a piece of onion, as in the diagram.
Mount it on a slide in a drop of water. Avoid wrinkling the tissue. Add a cover slip to your wet
mount. Examine the living cells under low power. Place a drop of iodine stain next to the cover
slip of the wet mount. Next, place a small pierce of paper towel next to the cover slip on the slide
opposite the drop of iodine stain. As the towel absorbs water, the iodine stain will be drawn under
the cover glass. Select one cell under low power that shows the contents clearly. Move it to the
center of the field of view. Turn to the high power objective and focus with the fine adjustment
knob. Draw an onion cell and label the cell wall, cytoplasm, nucleus, nucleoli, and cell
membrane.
1. What is the shape of the onion cell?
2. What was the color of the living cytoplasm before you stained it?
3. What effect does the stain have on the nucleus of the onion cells?
4. Why are there no chloroplasts in the onion cells?
B. Elodea Cells
Prepare a wet mount of a whole Elodea leaf. Examine the leaf under the low power. Select a
portion of the leaf where the cells are very distinct. Center this portion in the field of view and
focus it under the high power. Use the fine adjustment knob to focus up and down on the various
depths. As you turn up and down a new layer of cells will come into focus. Note how many layers
of cells there are in the leaf. Can you see any movement of the chloroplasts in the cell? Draw and
label the cell wall, cell membrane, cytoplasm, and chloroplasts, in an elodea cell. (The nucleus
is hidden under the chloroplasts).
1.
Do you see movement of the chloroplasts?______ If you see movement, are they moving
in the same direction? _______ The movement of the chloroplasts is due to movement of
the proteins in the cytoskeleton. Movement of the cytoplasm is called cytoplasmic
streaming. What would be an advantage of chloroplast movement?
______________________________________________ (Hint: What energy source do
chloroplasts need for photosynthesis?)
2.
How many layers of cells are found in the Elodea leaf?
C. Potato Cells
Use the potato peeler to shave a thin piece from a potato. Cut off, at the thinnest portion, a piece
about the length of a pencil eraser. Place this thin tissue in a drop of iodine on a slide and add a
cover slip. Examine the slide under low power. Note the blue-black spheres; they are leucoplasts
that are loaded with starch grains. Draw a potato cell; label the cell wall and leucoplasts.
What is the most obvious difference between a potato cell and an elodea cell?
D. Euglena Cells
Using a medicine dropper, add one drop of the Euglena culture to a clean slide and add a cover slip.
Locate a Euglena low power (yellow band on objective). Watch the organisms swim around. Find
one cell or a group of them that are not moving and switch to high power. Draw a cell. If you need
help, use the pamphlet provided. Label the flagellum, chloroplasts, and nucleus.
1.
Are Euglena prokaryotes or eukaryotic cells? ________________________ How do you
know?
2.
Near the flagellum is an eyespot that can lead the Euglena to light. Why is the eyespot a
good adaptation for a Euglena?
3.
Are Euglena unicellular (one celled) or multicellular organisms?
5.
What Kingdom have scientists created for Euglena and its relatives?
II.
Analysis
1. Cell Part
Plant,
Animal,
or Both
Function
Site of cellular respiration; food is broken down releasing energy to
make ATP
of photosynthesis, the transfer of light energy to chemical energy
(glucose)
Intracellular digestion of worn out cell parts and
Food
Control center of the cell; contains hereditary information
Site of protein synthesis
Channels for transport of protein & lipid
Collects, packages, modifies, and secretes (repackages) protein
Stores food, water, and other needed materials and wastes
Long projections; used for locomotion; are found on protozoans
Structure and support in plant cells; made of cellulose
Short, hair-like projections used for locomotion in protozoans
2.
What three structures are found in plant cells, but not in animal cells?
3.
What is the outer covering of a plant cell?
4.
Does a plant cell have a cell membrane?
5.
Do plant cells have lysosomes and centrioles?
6.
How is the presence of the cell wall made of tough cellulose fibers an adaptation for plant
cells?
7.
Which cell part has the following nick-name?
a. The power-house?
b. The gate-keeper?
c. The pan-cake?
d. The suicide sack?
8.
The structure of an organic molecule, organelle, and cell is related to its _________.