Name___________________________Partner________________________Computer number_______
Applying Cell Knowledge
PURPOSE
The purpose of this lab is to introduce you to the wide variety of living cells that exist. Cells can be very
tiny and have no real organelles (cell membrane, cytoplasm, DNA, ribosomes), or they can have a very
elaborate structure that includes a nucleus, organelles, long filaments and even propellers. Keep in
mind that all of the monomers of the molecules we have talked about to date are small enough to get
through the membrane and into even the smallest cells!
We will use several websites to get started. First go to
http://micro.magnet.fsu.edu/primer/virtual/magnifying/index.html
This website (from Florida State University) shows how a microscope can
magnify images. The picture you see (in the big circle) is a
microprocessor chip from a computer. It is already magnified 25
times. The real size of the chip is shown to the left the tiny blue
square. Since this is Biology class, we don’t really want to look at microchips, so
below the large circle you will see the words
Choose a Sample : Choose Onion Cell Mitosis.
So the actual cells picture that labeled “actual size”. Recreate this picture (in the correct size) below.
This is what you can see of an onion root tip WITHOUT magnification. Seems pretty insignificant,
doesn’t it?
1. Now look at the 25x magnification (it’s in the big circle that is purple and black). The dark spots
you see represent the nucleus within a cell. Based on the “dark spots” estimate how many cells
you can see.
a. 10 or 20
b. More than 20 but less than 100
c. More than 100 but less than 1000
d. More than a thousand
2. You should be able to make out the outline of the cell (look at the cells at the top. Draw about
10 cells to scale (in other words draw them the same size that you “see them”. They are quite
small. (the circles are the nuclei, NOT the cell!. Use a sharp pencil to draw this small picture
1
Name___________________________Partner________________________Computer number_______
3. Now look at the 100 magnification. The circle is called the field of vision. How many cells do
you see now?
a. 10 or 20
b. More than 20 but less than 100
c. More than 100 but less than 1000
d. More than a thousand
4. How many times more magnified are these cells than the 25x cells? _________. Based on this,
estimate how many cells were in the 25x field of vision and compare that to your estimate.
5. Once again, draw about 5 cells to scale (that means the same size as they are on the screen).
6. Now jump to 500 magnification. Did your field of vision (the number of cells that you can see)
increase or decrease? _________________ Did the magnification increase or decrease?
_____________ Write a statement that relates field of vision and magnification.
7. We can see now that some cells have no nucleus (they are in the process of dividing), some
have dark circular defined nuclei, while others have “snake like” features (these are
chromosomes). Draw a picture that contains 5 cells making sure that at least one of the three
different cells mentioned is drawn (once again drawing them to the actual size you see in the
field of vision. And draw them “beside each other” as you see them (I don’t want “boxes with
circles” or “squiggles”. DRAW!!!
2
Name___________________________Partner________________________Computer number_______
http://learn.genetics.utah.edu/content/cells/scale/
Cells vary in size and shape. This “animation” (sort of) compares a variety of cells The units
used in diagram are metric. Amoeba, paramecium and human eggs are very large cells. Write
their measurements in the space below. The unit is micrometers (the m looks like a script u).
The relative size ranges of biological things is shown in Figure 1 (next page) . The boxes
represent ranges (human cells are 2-500 m).
How many times bigger is an egg than a sperm (the head of the sperm is only about 5
micrometers)?
How many times larger is an egg cell compared to a skin cell?
How long is an E. coli (use the length measure) as compared to a RBC? A skin cell?
Finally how big is a virus compared to a skin cell?
A micrometer is a thousand times smaller than a millimeter (mm). A cell membrane is 0.003
micrometers or 3/1000 of a micrometer. The unit for 1/1000 of a micrometer is called a
nanometer, so a protein is about 3 nanometers.
1. Look at the chart (Figure 1) below. The blocks at the top of the chart indicate the range
(in size) for human cells, bacterial cells and viruses. What is the size range for human
cells
2. What is the size range of bacterial cells in micrometers? Is this larger or smaller than
human cells? What is the size range in nanometers (think, what would you need to
multiply by). All units are micrometers (m.. the funky letter is the Greek letter mu)
3
Name___________________________Partner________________________Computer number_______
3. What organelles are the same size as bacterial cells?
4. Is it possible to have a large virus that is the same size as a small bacteria? What range
represents the overlap of size of bacteria and viruses?
5. Can you see an ‘average’ human cell with just your eyes?
6. What would you be able to see (look at all parts of the chart) with a light microscope (which is
the type of microscope that we will be using).
7. What type of microscope would you need to see ribosomes and proteins?
4
Name___________________________Partner________________________Computer number_______
8. Can we see a hydrogen atom?
CELL SHAPE – Figure 2a.
Figure 2b.
The shapes of cells are quite varied with some, such as neurons, being longer than they are
wide such as erythrocytes (red blood cells) being equidimensional and yet others having special
shapes and fibers to allow contraction (muscle).
Some cells are encased in a rigid wall (like plant cells), which constrains their shape. This is
important in plants because they take in a lot of water and it prevents the cell from getting too
large and breaking. In plants, the cell wall also acts as a filter, allowing the passage of water,
CO2, small proteins and other small molecules, but nothing larger.
The size of cells is also related to their functions. Eggs (or to use the latin word, ova) are very
large, often being the largest cells an organism produces. The large size of many eggs is related
to the process of development that occurs after the egg is fertilized. Until the fertilized egg has
a system of acquiring energy (like a bloodstream in humans), an egg must use a tremendous
amount of energy contained within this large cell to undergo a rapid series of cellular divisions.
All of this energy must be contained in the cell, or the material that surrounds it (like the yolk
and egg white of a chicken egg).
The structure of a cell and the function of that cell are linked. There is a saying that Form fits Function.
Cells are designed differently because they do different things.
5
Name___________________________Partner________________________Computer number_______
1.
Figure two shows three different types of cells a) Red blood cells, b) muscle cells and c) nerve
cells.
a. What is the function of red blood cells? Why does having a “rounded edge” help its
function?
b. What does a nerve cell do? Why does having a long axon and many dendrites help it to
function?
2. Plants have interesting cell names: (go back and look at diagram 2b). Look up collenchyma,
parenchyma and sclerenchyma, and sclereids.
a. Describe the structure of each, and an example of where each is found
b. Describe the function of each
c. Explain how the form (structure) fits the function.
6