Download THE BASIC UNIT OF LIFE

NAME_______________________________DATE______________MOD______
THE BASIC UNIT OF LIFE-IDENTIFYING CELL ORGANELLES
PRE-LAB DISCUSSION:
The cell is the basic unit of life and the individual part of which the whole
organism is composed. The cell is the smallest unit that can perform all life functions.
Many of the substances in a cell are organized into specific organelles. Although all cells
have certain characteristics in common, cells can vary in size, shape, and structure and
thus function.
PURPOSE:
1. To observe a variety of living and once living material under the microscope.
2. To determine if these materials do or do not show a cellular type of organization.
3. To study and locate under the microscope six or seven specific cell parts-cell wall, cell
membrane, cytoplasm, nucleus, nucleolus, chloroplasts, and large central plant vacuole.
4. To compare and contrast animal cells and plant cells
MATERIAL:
microscope
dropper
white onion
salt water
microscope slides
toothpick
Elodea plant
Distilled water
coverslips
methylene blue stain
iodine stain
purple onion
LAB DRAWING PROCEDURE:
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Your name and period should appear on top of every page you turn in.
All drawings will be on unlined paper. No more than four drawings per page.
All drawings will be on one side of the paper only.
All drawings must be in pencil.
All drawings done through the microscope are to be in a circle.
All drawings not done through a microscope are to be in a square.
All drawings should have a title and magnification under them.
All drawings should be carefully labeled using straight lines (no arrows) that are
parallel to the top of the page and do not cross over any other line.
All drawings should be in “color book style.”
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LAB PROCEDURE:
PART A. CELL MEMBRANE, NUCLEUS, NUCLEOLUS AND CYTOPLASM:
Human cheek cells may be used for viewing the cell membrane and cytoplasm. A
cell membrane is a thin outer boundary that surrounds the cell and separates it from the
external environment and from neighboring cells. Cytoplasm is the jellylike inner portion
of the cell between the nuclear envelope and cell membrane.
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Place a drop of methylene blue stain onto a slide. CAUTION: Methylene blue is a
skin and eye irritant and may stain clothes. Be careful not to spill or drop the bottle.
Call the teacher if spillage occurs. Wash hands or flush eyes with water for 15
minutes if contamination occurs and call the teacher. Wear eye goggles when using
methylene blue.
Gently scrape the inside of your cheek with the flat side of a toothpick (do not gouge
your cheek). You will not be able to see anything on the toothpick when you remove
it from your mouth.
Dip the toothpick into the stain on the slide and mix once or twice.
Add a cover slip and examine the cells under low and high power of your microscope.
Locate and examine cells that are separated from one another rather than those that
are in clumps.
Use a separate piece of paper to draw several cheek cells as they appear under high
magnification or the highest magnification with a good view. Label the cell
membrane, nucleus, nucleolus and cytoplasm.
PART B. CELL NUCLEUS, CELL WALL, AND NUCLEOLUS:
White onion cells may be used to show a cell’s nucleus and nucleolus. These two
structures appear within most living cells. There may be several nucleoli (plural of
nucleolus) appearing as tiny dots within each cell’s nucleus. The nucleus will appear as a
round structure inside each cell.
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Snap an onion bulb scale in half.
Use your fingernail to peel off a thin layer of onion tissue (the cell layer must come
from the inside surface).
Place one thin onion layer onto a microscope slide.
Uncurl or unfold any overlapped portion of the cell layer. Make sure that the layer is
perfectly flat.
Add a drop or two of iodine stain to the onion. CAUTION: Iodine is a skin and eye
irritant and may stain clothes. Be careful not to spill or drop the bottle. Call the
teacher if spillage occurs. Wash hands or flush eyes with water for 15 minutes if
contamination occurs and call the teacher. Wear eye goggles when using iodine.
Add a coverslip to the stained onion. Tap the coverslip gently with the eraser end of a
pencil to drive out any air bubbles.
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Observe the cells under both low and high power of your microscope. Note the brick
wall appearance of the cells with cell walls separating cells.
Locate a small round structure, the nucleus, within each cell. Examine the nucleus
carefully by focusing up and down through the cell.
With high power, observe the tiny dots or eyelike structures within the nucleus. These
are nucleoli. The outer edge of the nucleus is made up of a thin covering called the
nuclear membrane.
Draw a single onion cell on a separate piece of paper as it appears under high power
or highest power with a good view.
Label the cell wall, nucleus, nucleolus, and nuclear membrane.
PART C. CHLOROPLASTS:
Another cell part found in plants and algae is the chloroplast. Elodea, a common
water plant, shows these important structures well.
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Remove one leaf from a sprig of Elodea and prepare a wet mount slide.
Using low power of your microscope, position your slide so you are looking near the
edge of the leaflet.
Locate green, oblong cells. Examine these cells under high power.
Note the small green organelles inside each cell. These are chloroplasts.
Movement of the chloroplasts within the cell often can be observed. Attempt to locate
moving chloroplasts.
Draw a single Elodea cell on separate piece of paper. Use high power.
Label cell wall and chloroplast
PART D. VACUOLE
Vacuoles are particularly large and common in plant cells. It is a membrane
bounded fluid filled sac. In purple onion cells the vacuole contains the deep red, blue, or
purple pigment known as anthocyanin (this is the same pigment found in cabbage juice
that we used as a pH indicator).
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Use your fingernail to peel off a thin layer of onion tissue (the cell layer must come
from the outer purple skin of the purple onion bulb’s leaf scales).
Place one thin onion layer onto a microscope slide.
Uncurl or unfold any overlapped portion of the cell layer. Make sure that the layer is
perfectly flat.
Prepare a wet mount slide and observe the cells under both low power and high
power of your microscope.
To help distinguish the vacuole, add a few drops of salt water and observe, then add
distilled water and observe again.
Locate the cell wall, cytoplasm, nucleus, and vacuole.
Draw two or three purple onion cells on a separate piece of paper as it appears under
high power. Make two drawings, one as seen in salt water and the other as seen in
distilled water)
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Label the cell wall, cytoplasm, nucleus, and vacuole.
FILL IN TABLE BELOW:
Comparing Animal and Plant Cell Organelles
Parts we found in all cells
Parts only found in animal
Parts only found in plant
cells
cells
Finally, clean up! Rinse off all your slides in the sink. Set the coverslips on one
paper towel and the slides on another.
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