Download Cells lab - West Ada

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Cells lab
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Discussion:
Ever since Anton van Leeuwenhoek studied pond water and discovered “animalcules”, biologists have been interested in studying
the cellular organization of all living things. Van Leeuwenhoek was not the first to observe these microscopic structures. In 1665
Robert Hooke looked at cork and found tiny chambers or “cells”. After hundreds of years of observation, the cell theory was
developed. Biologist began to understand that all living things are composed of cells, cells are the basic units of structure and
function in living things and new cells are produced from existing cells.
Cells can be classified by the organelles, or specialized structures that perform specific functions in the cell. All cells have a cell
membrane and cytoplasm. Some cells contain a cell wall to protect the membrane, as in plants. Most cells also have a nucleus
unless they are a prokaryotic cell. Prokaryotes are small and simple cells like bacteria. Eukaryotes are another category of cells.
These cells are more complex and contain many organelles including a nucleus. Eukaryotic cells construct multicellular organisms
like plants and animals.
Plants and Animal cells are both Eukaryotic but they have different organelles. A Plant cell contains three extra organelles such as
chloroplast which helps harvest energy from the sun. Plant cells also have a cell membrane to prevent water loss and give structure
to stems. A vacuole is another organelle that plants have; it stores excess water and other materials like proteins, salts and
carbohydrates.
Problem:
How do Plant and Animals differ from each other?
Background Information:
1. Who discovered cells first Anton van Leeuwenhoek or Robert Hooke?
2. Name all 3 parts of The Cell Theory.
3. What is an organelle?
4. How is a Prokaryote different from a Eukaryote?
5. Give an example of an organism that has Prokaryotic cells and one of an organism with Eukaryotic cells.
6. Name three organelles a plant cell has that animal cells do not.
Hypothesis:
Describe what you think they will look like under the microscope.
Materials (per group of two):
Forceps, Dropper, Onion, Water, Microscope, Slide and cover slip, Toothpicks
Methylene Blue stain and Iodine stain
Procedure:
1.
2.
3.
ONION CELL
Peel the delicate transparent tissue from the inner surface of a piece of onion using forceps (tweezers).
Make a wet mount by adding a small drop of water on a glass slide; place the tissue, unwrinkled, on the water drop.
Add one drop of Iodine stain to the tissue and cover with a cover slip as directed.
Be careful - Iodine can stain and burn the skin!
4. Locate the onion cells at low power, focus only with coarse adjustment.
5. Next switch to medium power and focus with the fine adjustment. Switch to high power and focus with the fine
adjustment. Draw two of the cells at high power in your observation table.
6. Carefully clean and dry your slide and cover slip.
Procedure: ELODEA CELL
1. Make a wet mount by adding a small drop of water on a glass slide.
2. Obtain an Elodea leaf and place it on your slide.
3. Place a cover slip over the Elodea leaf.
4. Locate the Elodea cells at low power, focus only with coarse adjustment.
5. Next switch to medium power and focus with the fine adjustment. Switch to high power and focus with the fine
adjustment.
6. Draw two of the cells at high power in your observation table.
7. Carefully clean and dry your slide and cover slip.
Procedure: CHEEK CELL
1.
2.
3.
4.
5.
6.
7.
8.
9.
Using the flat end of a toothpick, gently scrape the inside of your cheek. The toothpick will have numerous cells attached to
it even if you do not see any.
Rub the toothpick (with the cells downward) on the center of a dry slide to create a cell smear. Dispose of the toothpick in
the garbage can.
Add 1 drop of methylene blue stain on top of the cell smear. Allow it to stand for 1 minute. (this stain will color almost
anything be careful)
Carefully place a cover slip over the smear-stain mixture.
To remove the stain from under the cover slip and replace it with clear water, place a piece of paper towel at the edge of
the cover slip and a drop of clear water at the edge of the cover slip opposite the paper towel. The stain under the cover
slip will be drawn up by the paper towel and clear water will flow under the cover slip to replace it. When finished discard
the paper towel in the garbage can.
Using low power, locate a few cheek cells under the microscope (remember to focus using coarse adjustment only)
Next switch to medium power and focus with the fine adjustment. Switch to high power and focus with the fine
adjustment. Draw two of the cells at high power in your observation table.
Carefully clean your slide and cover slip, be sure the microscope is clean and dry, put low power down, run the stage down
and put the scope away.
Be sure your lab area and sink is clean.
WHEN YOU ARE DONE CLEAN ALL MATERIALS AND YOUR HANDS.
STAY AT YOUR WORK STATION.
RAISE YOUR HAND AND ASK YOUR TEACHER TO RELEASE YOU FROM THE LAB.
Conclusion: See back of your Lab Report
Analysis: See back of your Lab Report
Cells Lab
Name ________________________
Problem:
Period ________
Background Information:
Hypothesis:
Observations:
Drawing
Prokaryote or
Eukaryote
Nucleus
Yes or No
Cell
Membrane
Yes or No
Cytoplasm
Yes or No
Onion Cell
Elodea Cell
Cheek Cell
Initials:
Background Information
Clean Workstation
Cell Wall
Yes or No
Chloroplast
Yes or No
Vacuole
Yes or No
Conclusion:
Summarize the procedure you followed for each slide. Was your hypothesis correct? What did each cell look like? Describe the cells
in detail. Include organelles that were visible from the microscope.
Analysis:
1.
Which cells had a nucleus?
2.
Where were the nuclei generally found?
3.
What are the green structures observed in the elodea?
4.
Why didn’t the onion cells have the green structures?
5.
What is the shape of an onion cell?
6.
Why is this shape good for constructing plant tissues?
7.
What is the shape of a human cheek cell?
8.
Why are stains such as methylene blue and Lugol’s iodine used when observing cells under the microscope?
9.
In general, the surface of a tree has a harder “feel” than does the surface of a dog. What cell part does the plant cell have
that accounts for this difference?
10. If you were given a slide containing living cells of an unknown organism, how would you identify the cells as wither plant or
animal?