Lab 4 Microscope Usage, Cell Structure, Diffusion and Osmosis
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Cells have three ways to get things in or out: Diffusion, Osmosis, and Active Transport. In this
lab you are going to become familiar with how microscopes work and in doing so explore the
inner workings of individual cells.
Pre-Lab Questions
1. Explain the concept of diffusion and provide an example.
Diffusion is a concentrated substances of movement were it can move to a area where its less
concentrated or move to a area where its more concentrated. For example , when making
spaghetti noodles the water diffuses them by making them bigger and tender an moist.
2. Explain the concept of osmosis and provide an example.
Osmosis is a permeable membrane that simply diffuse water over a particular area. For
example, when taking a bubble bath and your relaxing for while and you notice that your
hands and toes and soggy or shriveled up its because the water is less concentrated which
causes osmosis to get into the body.
3. Explain the concept of active transport and provide an example.
Active transport is a concentrated cell that sends protein to move a substance against its own
cocentrated gradient from where its less concentrated to where is more concentration taking
place. An example of active transport is sodium being forced into the cell membrane.
4. What is a concentration gradient? What role does a concentration gradient play in diffusion
and osmosis?
Concentrated gradient is basically area that is more concentrated than the other area. The
role that concentration gradient play diffusion and osmosis is that it allows the movement
between the two from less concentration or high concentration.
5. Explain the concept of semi-permeable membrane. Provide an example of what can and
cannot get through a plasma membrane.
The concept of semi-permeable is that some things such as water or particles can cross the
membrane. For example what can get through the plasma membrane is water, but solutes
cannot pass.
Click here for the lab activity. http://bio.rutgers.edu/~gb101/lab1_cell_structure/index.html
Read the Objectives and Instructions then click on “Begin Assignment”.
On the next page, click on “Click here to get a microscope”
Read through and follow the directions to
familiarize yourself with how to navigate the
virtual microscope.
The controls for zoom in, zoom out are located at
the bottom of the microscope image. They are
noted here with the big red arrow. I thought they
were a little difficult to find at first so this just
shows you where to look. On the website there is
not a big red arrow.
Once you have figured out how to operate the microscope click on “Continue” found in the
left frame.
6. How do you determine the total magnification?
To determined the total of magnification you'll simply multiply the ocular lens by objective lens
to get the total magnification.
7. Do you have to use the objective lenses in any specific order? If so, what is the
order?
Yes there is specific order first at the lowest magnification of the object you'll se that it only
occupies only a small portion of the field. Then at the highest magnification the object nearly
fills the field. Now you'll you use a mathe matical formula to determine the field size.
Continue working through the website learning about field of view and image formation.
8. As you increase magnification, what happens to the field of view?
As you increase magification on the block on the graph gets larger.
Examining Cells Microscopically
The Elodea Plant. This aquatic plant is easy to work with and allows you to see several
subcellular structures found in plant cells. To examine the elodea leaf cells you have to click on
the hyperlinks in the left frame. They are the ones in blue. Begin with scanning and work your
way through the instructions.
9. What two subcellular structures can you see in the elodea slides? What is the
function of each of them?
You can see the cytoplasm of cell it wasnt static, but it was around the perimeter of the cell.
And also the chlorplasts which were carried by the streaming of the cytoplasm.
Continue on to the Onion Epidermis Slides.
10. What two subcellular structures can you identify in the onion slide? You’ll
need to click on the “field diameter” link to see the correct slide.
The visibility of nucleus, cytoplasm, and vacuole may appear if the amount of light is reduced.
Continue on to the animal cell slides
11. What does the condenser diaphragm control on a microscope?
Condenser diaphragm controls the amount of light being redirected on a specimen.
Adjust the condenser diaphragm by following the directions for using your mouse.
12. When you move the condenser diaphragm what happens to the image?
When you move the condenser diaphragm It changes image and contrast you are viewing.
Click on the higher magnification link
13. What two subcellular structures can you identify in this human cheek cell
slide? Provide the function of each.
Is example of animal cell and simple squamous epithelium by little amount of material scrap
from the mouth area and water on the glass slide.
14. The following diagram is the same as the protist Euglena on the website.
Identify the structure and functions for each structure A-D:
Structure
Function
A
Flagellum
Allows the cell to move.
B
Nucleus
The central of euglena.
C
Chloroplast
Photosynthesis.
D
Eyespot
detects light.
Diffusion and Osmosis
Materials move by diffusion and osmosis constantly. Man has used their knowledge of these processes to
preserve food. That’s what allowed man to transition from being nomadic hunter gatherers to setting up
stable agrarian communities. In order to stay in one place, there had to be a way to preserve food so it was
available year round. Salt and sugar have been used for centuries to preserve food. This works because both
salt and sugar are able to bind to water. All organisms, even bacteria, require water. Bacteria are
generally 80-90% water. Below are two different scenarios of bacteria in different environmental conditions.
For each scenario you are given what the bacterial organism is composed of and what is in the proposed
environment. You have to look and compare what the bacteria is made of with its environment and determine
for each substance if it will move into or out from the bacteria. Once you have made your determination, fill in
the table with your answer of will the substance move, by what process, and in which direction. In the first
scenario, the S. aureus cell is 82% water while the marinade is 20% water. With more water inside the cell
than outside, you woud expect the water to move from the cell into the marinade. So there would be movement,
osmosis, out from the S. aureus.
15. Staphlococcus aureus is made up of 82% H 2 O, 3% NaCl, 1% KCl, 12% Protein, 2% Nucleic
Acid. A company makes and bottles a special marinade that consumers use to prepare food for
grilling. The marinade consists of 50% NaCl, 10% Pepper, 20% Vinegar, 20% H 2 O. For each
of the following substances, indicate whether or not it would move, by what process would it
move (diffusion or osmosis) and in what direction it would move (into or out from S. aureus).
S. Aureus
Substance
H2 O
NaCl
KCl
Protein
82% Water
3% NaCl
1% KCl
12% Protein
2% Nucleic Acid
Movement
Yes or No
50% NaCl
10% Pepper
20% Vinegar
20% Water
Process
Diffusion or Osmosis
Marinade
Direction
Into / Out from S. Aureus
16. Would S. aureus survive if it contaminated a vat of this marinade? Why or why not?
17. E. coli is made up of 84% H 2 O, 3% NaCl, 1% KCl, 9% Protein, 3% Nucleic Acid. Pond
water composition is 84% H 2 O, 3% NaCl, 2% KCl, 11% Minerals, soil. For each of the
following substances, indicate whether or not it would move, by what process would it move
(diffusion or osmosis) and in what direction it would move (into or out from E. coli).
Pond
84% Water
3% NaCl
2% KCl
11% Minerals
E. coli
84%Water
3% NaCl
1%KCl
9% Protein
3% Nucleic Acid
Substance
Movement
Yes or No
Process
Diffusion or Osmosis
H2O
NaCl
KCl
Protein
18. Can E. coli survive in this pond? Why or why not?
Direction
Into / Out from E. coli