Name: ____________________
Period:__________
Identifying Dominant Organelles Lab
Read this introduction carefully!:
Not all cells look the same. Although your textbook has many images of cells that include every organelle
ever discovered, in reality, no cells like these exist! This laboratory exercise deals with complex types of cells,
real cells found in animals and plants. These cells are all eukaryotic, but as you will see, none of them resemble the
“perfect cells” found in your textbook illustrations. Each cell has dominant structures that dictate its function; the
dominant organelle is typically related to the function of the cell. Dominant organelles are not necessarily the
largest in the cell, but are typically the most plentiful. REMEMBER: CELL STRUCTURE = CELL FUNCTION! Cells
within an organism work together to make important processes happen. The idea that all cells have specialized
function is similar to how your body works; your body is composed of functionally distinct organs that are
functionally dependent upon one another. Each cell in a multi-cellular organism has a specific set of functions.
Therefore, each type of cell will contain different organelles (or organelles in different levels of abundance),
appropriate for its specific functions. For example, muscle cells contain a lot of mitochondria while leaf cells and
root cells in plants do not.
Prelab Questions:
1.
Use your textbook or internet resources to look up the parts of the cell theory and record them below. Explain
how and when it was developed and who was involved.
2. Use your textbook or notes from class to record the major differences between eukaryotic and prokaryotic
cells below:
3. Goblet cells (seen embedded in surrounding tissue in the picture below) in your lungs are responsible for making
mucus (rich in proteins) that coats your respiratory tract. The proteins are manufactured at the ribosomes
attached to the endoplasmic reticulum and modified inside the endoplasmic reticulum. The proteins are then
transported to the Golgi apparatus for packaging and then shipped to the cell membrane in vesicles. The mucus
is then released outside the cell and coats your lungs.
Draw in the types of organelles that would be found inside the open goblet cell. Make sure to label your
drawings.
Goblet Cell outlined below
4. Now that you know what goblet cells from
#3, lets take a look at other cells in the
lungs. Goblet cells are labeled as the letter J
in the picture shown. Take a look at the
other longer cells labeled I, these are called
columnar cells. The columnar cells all over
cilia on one end of the cell (labeled in the
picture as H). Using your critical thinking
skills, propose an explanation for why these
cells would need to be covered on one end in
cilia.
Relating Cell Form to Cell Function
1.
Elodea Leaf Cells (Wet Mount):
a.
What is the function of a leaf cell in a plant?/What is the major process going on here?
b. What organelle would you expect to find in abundance in a leaf cell?
Select a single young green leaf from near the tip of the water plant elodea (elodea may be found at the teacher’s
lab station) and prepare a wet mount. Begin your observations on scanning power, then move to low and finally high
power. By carefully focusing up and down using only the fine adjustment, you should be able to see that the leaf
consists of several layers of brick-shaped cells.
c. Carefully, determine how many cell layers deep the leaf is.
At the outer boundary of the cytoplasm is the cell or plasma membrane. You will be unable to see this due to its
close contact with the cell wall, which is visible. You will be able to see many small green bodies called chloroplasts
in each of the cells. They are suspended in the cytoplasm, a clear fluid immediately within the cell membrane. By
focusing through the center of one cell (as opposed to the upper or lower surface of the cell) you should be able to
determine that a large, fluid filled vacuole almost fills the cell while the cytoplasm and the chloroplasts are
restricted mainly to the periphery. If you observe the upper or lower surface, you will see many chloroplasts
streaming near the surface. Since the vacuole is separated from the cytoplasm of the cell by a thin vacuolar
membrane, a distinct boundary between cytoplasm and vacuole will not be visible with your light microscope. In this
unstained cell, the nucleus, which is much larger than a chloroplast, is colorless and very difficult to see.
d. Make a drawing of a single elodea leaf cell showing the central vacuole, nucleus (if visible), cell wall, and
chloroplasts. Also identify where you would expect the cell membrane to be located.
e.
Do you see evidence of structure relating to function in the elodea cell? Please explain.
2. Potato Tuber Cells (Modified Stem) (Wet Mount):
a.
What is the function of this modified stem cell in a potato plant?
b. What organelle would you expect to find in abundance in a potato tuber cell?
Carefully remove a very thin slice (onion-skin thin and almost transparent) of potato tuber from the material
provided on the teacher’s lab station. Be very careful when cutting the potato with the razor blade and when
cleaning the razor blade. After cutting your potato slice, rinse the slice carefully with water to remove excess
starch grains adhering to the surface. Mount the selection on a slide and stain with a drop of iodine, cover it with
a cover slip, and observe the edge of the specimen under all objectives of the microscope. The iodine will stain the
starch grains purple or black. Look between the starch grains for cell walls, which appear as clear to gray lines.
c.
Make a labeled outline drawing of a single potato tuber cell showing several starch grains, the
leukoplast and the cell wall.
d. Do you see evidence of structure relating to function in the elodea cell? Please explain.
3. Pancreatic Cell in the Pancreas of a human:
a.
What is the function of a pancreatic cell in a human?/What is the major process going on here?
b. What organelles would you expect to find in abundance in a pancreatic cell?
Examine the photomicrograph of
the pancreatic cell.
c.
Make a sketch of the picture and label the following organelles: mitochondria, Golgi Apparatus and
Endoplasmic Reticulum, Vesicles, Nucleus, Nuclear Membrane, and Nucleolus. (Note: This is part of a
cell and therefore the cell membrane is not visible.)
a.
Do you see evidence of structure relating to function in the pancreatic cell? Please explain.
4. Monocyte – A type of white blood cell:
a.
What is the function of a white blood cell in a human?/What is the major process going on here?
b. What organelles would you expect to find in abundance in a white blood cell?
Examine the photomicrograph of the monocyte (the large cell
in the middle is the monocyte, it is surrounded by smaller red
blood cells.
c.
Make a sketch of the picture and label the following organelles: Lysosomes, Cell Membrane, Nucleus,
and Nuclear Membrane. (Note: This cell’s nucleus contains a U shaped nucleus. The small dark dots
represent the lysosomes.)
b. Do you see evidence of structure relating to function in the pancreatic cell? Please explain.