Plant and Animal Cells

subject = Honors Biology
title = PLant and Animal Cells

Plant and Animal Cells

I. Introduction

All organisms in life are composed of at least one or more
cells. Cells are the basic units of life. There are three main
features of a cell. First, all organisms consist of one or more
cells. Second, cells are the smallest units of life and third,
cells arise only from preexisting cells. These three facts are
referred to as the cell theory.
All cells can be categorized into two basic cell types.
They are prokaryotic and eukaryotic. To distinguish where cells
are placed in the two categories, what is inside the cell must
first be looked at. Every cell, either prokaryotic or eukaryotic
all contain basic cell parts. They are: a plasma membrane,
cytoplasm, DNA (the genetic material), and ribosomes.
Prokaryotic cells have a simple structure and they are usually
smaller than eukaryotic cells. Also, most prokaryotic cells
contain a cell wall. In addition to having the basic cell parts,
eukaryotic cells also contain a membrane-bounded nucleus and cell
organelles. The membrane surrounding the nucleus in eukaryotic
cells, separate the nucleus from the cytoplasm.
Most of the cells we used in the experiments held, were
multicellular or consisting of more than one cell. A variety of
cells were used in completing the experiments. We used union
cells, cheek cells, potato cells, and Elodeo cells. We also used
Planaria which is a unicellular organism. Many stains and dyes
were used in the experiments. They were water, methylene blue,
salts, and iodine.
In our studies of cells, we conducted three experiments to
test the different features of cells. The first two experiments
were on how membranes were selectively permeable, diffusion, and
osmosis. To test this, we set up two experiments. The first
experiment we set up had three cups. In each cup a potato slice
and a different liquid was put in. In the first cup was filled
with distilled water. The second cup was filled with salt water
and the third was left empty. We left these cups sit for twenty-
four hours and then we observed them.
The second experiment we set up involved dialysis tubing
which was acting like a membrane. In the dialysis tubing we put
a liquid that was made of starches and sugars. We then put the
dialysis tubing into a beaker of water which had a few drops of
iodine. We left this over time and observed it.
Our third experiment dealt with the different parts of a
cell. To complete this we had to make wet-mount slides and
observe them under a light microscope. To prepare a wet-mount
slide you must first obtain your specimen you are going to look
at. You then put the specimen on a clean glass slide in the
middle. Next, you take a medicine dropper and place one drop of
water on the specimen. After that, you hold a clean coverslip
and place the bottom edge of the coverslip in the drop of water.
Next, slowly lower the rest of the coverslip so that there are no
air bubbles, onto the remaining part of the specimen. By putting
specimens into wet-mount slides it saves a lot of time and energy
instead of putting them into set slides. Also, a wet-mount slide
can be cleaned and re-used.
We put onion cells, cheek cells, and Elodeo cells into wet-
mount slides. After we made slides for each one we observe them
under the microscope. For some of the cells, we had to apply a
dye to have make the cell more visible under the microscope.
Methylene blue was applied to the cheek cells and iodine to the
onion cells. To see the cheek cells, we had to reduce the amount
of light coming into the microscope. We had to do this because
when we reduced the amount of light, we could see the cells more
clear. Elodeo cells were observed as a wet-mount slide and also
with salt water. To apply a die to a previously made wet-mount
slide, an edge of the coverslip must be lifted just enough to get
the dropper under the apply the dye. At first, some of the
epidermal cells of the onion were folded. This indicates that
the cells were thick and there was more than one layer of cells.

II. Discussion

In the experiment involving the three cups and the potato
slices, we observed the different amounts of turgor pressure. In
the cup with the distilled water, the turgor pressure increased.
Turgor pressure is the internal pressure that results from being
filled with water. The potato slice