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Biology Students and the Giant Plant Cell 

Biology Students and the Giant Plant Cell  by Judith D. Jones
East Chapel Hill High School  

Teacher Introduction:

A traditional activity in a high school biology class is to have students create cell models. I have found that one drawback to this activity is that the organelles are always greatly enlarged relative to the size of the cell. A similar problem exists with cell diagrams in textbooks. Students are misled into thinking that the organelles are very large. The following activity involves students in creating organelles to scale for a Giant Plant Cell (approximately 3 meters on each side) made out of clear plastic painter's drop cloths and inflated with inexpensive portable fans (see provided instructions for making the big cell). Students use ratios in order to determine how large their organelles should be--a good integration of math into the biology curriculum (student activity included).

This activity has several advantages. Students are engaged in very active learning and they enjoy the mystery surrounding the arrival of the Giant Cell.** They can conduct their research using many sources, including the Internet. They must problem solve as they decide what size their organelles need to be and what materials will best represent the infrastructure of the organelles. They collaborate to prepare an interesting presentation for the rest of the class which taps into their ability to communicate and their creativity. After students have been actively involved in problem solving, they make a very intent audience for their peers because they are intrigued by how other people solved similar problems. The students come away with a very clear visual image of the proportions of cell parts and the functions of these structures. 

Suggested Classroom Activities

  1. Students are presented with the problem of "The Giant Plant Cell." Students are organized into groups of two or three. Each group signs up for an organelle.
    • nucleus and nucleolus
    • mitochondrion
    • chloroplast
    • rough endoplasmic reticulum (focus on function of ribosome)
    • smooth endoplasmic reticulum (focus on function of ER)
    • Golgi complex
    • lysosomes
    • peroxisomes
    • microtubules and microfilaments
    • vacuole
  2. Students research the structure and function of their chosen organelle.
  3. Students produce a blueprint describing how they will construct their model and its size.
  4. Students prepare a class presentation.
  5. The Giant Plant Cell arrives and students present their organelles.
  6. As students are presenting, other class members are taking notes on the presentations. The focus of these notes is the structure of each organelle, its function, and its role in the total functioning of the cell.
** The excitement is increased if the large inflated "cell" does not appear until the day of the presentation.


Helpful Notes:
  1. Some cell parts, such as the endoplasmic reticulum, microtubules/microfilaments, and vacuole are found extensively throughout the cell. Students should just make a section of such cell structures and then discuss in their presentations how extensive these structures are in the cell.
  2. Lessons on the cell wall and plasma membrane can be taught by the teacher. I explain that the drop cloth represents the plasma membrane and the ceiling and floor and one wall (which the drop cloth touches) represents the cell wall. Then I do the lessons on the functions of these structures including osmosis labs, etc.
  3. For students who need less direction, you can have them construct the cell and decide how they are going to create organelles to scale. Leave the discovery of the mathematical applications up to them. The instructions are precise. However, it is
    preferable to have students do as much of the problem solving as possible.

Following are:
  • Student instructions for constructing organelles to scale
  • A rubric for evaluating the student projects
  • A chart of actual organelle sizes (taken from various sources); students should do their own research)
  • Suggested questions for processing and/or evaluation
  • Instructions for building the giant plant cell 

The Story! You can create your own tale of the visit of the Giant Cell and how it lost its organelles. I enjoy spinning a new tale each year. One year I conjured up a "mad scientist" who had been experimenting with cells and with a machine that took microscopic things and created giants. Have fun with this! You can build the suspense and create interest. Don't tell them what the cell will look like - other than its dimensions.

Creating the Organelles The Giant Plant Cell is shaped like a giant cube that is 3 meters (300 cm) on each edge. You have been provided with a chart of actual cell organelle sizes. You must, using ratios, calculate the size of your giant organelle so that it is proportionately correct for the huge cell. You also need to research the function of the organelle in order to build it so that it can carry out its role in the giant cell. First, you will prepare an architectural design plan that will be evaluated by your teacher. Then you will build your organelle. You will prepare a 3-5 minute report to present to the class. Your organelle will be judged according to the accuracy of its size, the correctness of its details, your explanation of its function and your creativity. 

Equation for determining size of organelle:
Size of giant organelle = Actual size of organelle
Size of giant cell (300 cm)  = Actual size of average plant cell (30mm)


Organelle Architectural Design Sheet

Names of Design Team

__________________ __________________ ________________

Name of Organelle _______________________

Equation for determining the dimensions of giant organelle:








List of Materials Needed to Construct Organelle:

 

Material

Use












Diagram Showing Construction Plan:









Plan for Division of Labor Among Construction Team:


Grading Rubric for Colossal Plant Cell Organelle

Basic Requirements

  1. Construction of Organelle
    • All constructed organelles must be 3-dimensional.
    • All organelles must show internal and external details.
    • All organelles must be the correct size for the colossal plant cell.
  2. Oral Presentation
    • Reports should be about 3-5 minutes long.
    • Each member of the team should do part of the presentation.
    • The presentation should include details about the organelle's structure and function.
    • The presentation should include a discussion about how many of the organelles will be manufactured for the colossal plant cell.
    • The presentation should also include an explanation of the actual and giant size of the organelle.
RUBRIC USED FOR EVALUATION
(This should be given to the students at the beginning of the project.)
Note: The words (unacceptable, passing, acceptable, competent, and excellent) are used instead of A, B, C, D, and F.
  
Points  Criteria  Unacceptable  Passing  Acceptable  Competent  Excellent
30  detail -accuracy of the model There is no model or the structural details are completely wrong A few of the structural details represented accurately Most of the structural details are represented; some of them accurately All of the relevant structural details are represented; most accurately The structural details are all well represented and very accurate.
15  quality of presentation - explanation of structure and model Explanation of structure is inaccurate and incomplete; no reference to model made Explanation of structure is incomplete; very little reference to model Explanation of structure is good; very little reference to model Explanation of structure is good; there is reference to model Explanation of structure and reference to model are accurate, integrated and clear
15  Quality of presentation - explanation of function of structure Presentation is unclear and does not cover requested information Presentation does not cover all of the material; much of it is read Presentation covers all of the relevant material; much of it is read Presentation covers all of the relevant material; very little of it is read Presentation covers all relevant material; it is presented in a lively interesting fashion
20  individual participation Only one person in the group does the presentation; the parts may be connected or not One person does more than 70% of the presentation and the parts are presented separately One person does 60-70% of the presentation; the parts are presented separately Only one of the following is present; equal participation or connected parts Both people participate equally; the parts are well connected
10  size accuracy of the model Size is 100% too big or too small. Size is 75% too big or too small Size is 50% too big or too small Size is 25% too big or too small Size is within 25% of being correct
10  creativity  No evidence of creativity There is some evidence of an attempt to be creative but it is not executed well  There are a few creative details in the model or report  There are several creative details in the model and report The entire project shows evidence of creative thinking - both creation of the model and presentation.
100  Total 



v

Note: If a criterion is worth 30 points, then the numbers above the column chosen would be multiplied by 3. If the criterion is worth 20 points, then the number would be multiplied by 2.

Comments from Evaluator
** It is better if the students do their own research on these sizes, but the chart can be used if teachers are short on time.
CHART OF ACTUAL ORGANELLE SIZES
 

Cell or Organelle

Size in x (10-3 mm 

Average Plant Cell  30 x 
Nucleus  7.5-10 x
Nucleolus  2.5 x
Plasma Membrane  0.009 x thick
Mitochondrion  0.2-1 x wide x 3-10 x long
Chloroplast (other plastids are similar sizes) 2 x 5 x
Ribosome  0.025 x
Endoplasmic Reticulum (in most plant cells) 0.5 x thick (2 membranes of 0.009 mm with 0.03 mm compartment between them) 
Golgi Complex (dictyosome in plant cells) 1 x 1 x (membranes have thickness of ER)
Vacuole (central) sometimes serves as lysosome 50-80% of volume of cell
Microtubules  0.02 x diameter
Microfilaments  0.007 0.5-1 x diameter
Lysosomes (in some plant cells)  0.2-2 x
Peroxisomes  3 x
Cell Wall  1-2 x thick

Questions That May Be Used for Processing or for Evaluation of Understanding
  1. How is a typical plant cell the same as a prokaryotic cell? How is a typical plant cell
    different from a prokaryotic cell?
  2. How are plant and animal cells similar? How are plant and animal cells different?
  3. Discuss the interaction of the mitochondria and the chloroplasts. What substances do each produce that the other uses?
  4. Given the size of the organelles, which structures would you expect to see with a typical light microscope (magnifies 400x)? Explain your reasoning.
  5. How would a plant cell found in the petal of a flower be different from/similar to a "typical plant cell" such as the Giant Plant Cell?
  6. If the giant plant cell was a leaf cell, describe what you would need to add to the cell to help it function.
  7. Describe how proteins are synthesized in a plant cell.
  8. How is the cellular structure of terrestrial plants different from that of aquatic plants?
  9. If you were looking at a root cell, a leaf cell, and a stem cell what differences would you find?
  10. How is carbon cycled in a plant? In a plant cell?
  11. What happens to the molecules that are formed by the chloroplasts?
  12. What happens to the molecules that are formed by the mitochondria?
Instructions for Making the Colossal Cell

Each square is a 3m x 3m section of plastic painter's drop cloth; the squares are taped together down each seam with duct tape.

 

The left hand sides of sections 2 and 6 are taped to section 1 and the right hand sides of sections 2 and 6 are taped to section 4; section 5 covers the top and is taped to sections 2, 6, and 1; now you have a cube.


In one end of the cube, cut a slit to act as a door; tape all the edges of the slit. Hang a drape of extra drop cloth on the inside to cover the slit; this 
will keep air from escaping when you inflate the cell.


On the back of the cell, tape a tube of painter's drop cloth; tape one end of the tube around a fan so that the air blows into the cell. Cut an "X" into the cell so that the air can blow into it. 


Acknowledgements and Bibliography
Thanks to Richard Benz at Wickliffe High School in Ohio for the original idea for building a giant cell.
Thanks to Joe Lapiana in Massachusetts for the idea of putting an extra flap of plastic inside the doorway to prevent air loss.
Thanks to my colleague Gail Boyarsky for her generous enthusiasm in helping to carry out the activity.
Thanks to three years of UNC student teachers for their additions to the actual classroom activities - Christie Dobbin, Neeli Lambert, Christy Boylston, and Krista Blanton.
Bibliography
Curtis, Helena and Barnes, N. Sue (1989). Biology, 5th edition. New York: Worth Publishers, Inc.
Campbell, Neil A. (1993). Biology, 3rd edition. Redwood City. The Benjamin/Cummings Publishing Company, Inc.
Biological Science: An Ecological Approach, 7th edition (1993). Biological Sciences Curriculum Study. Dubuque. Kendall/Hunt Publishing Company.

 

Here is the entire class in the cell, comparing the sizes of their organelle models to the complete cell. While in the cell, I will explain how molecules get in and out of actual cells.




Here is a sample organelle. This is a wonderful nucleus. Note the black dots that represent nuclear pores on the nuclear envelope (skinny white balloons). The spiral balloons are the chromosomes - nice spiral touch. And the beach ball is the nucleolus - perhaps a little large. But this organelle showed very nice thinking and creativity in choice of materials.

 

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