Why Cells Divide
Part of Curriculum Unit:Diffusion & Osmosis - Trading Places
Abstract help
As the students learn the unifying concepts of diffusion and osmosis, they are ready to see the connection to the exchange of nutrients and wastes into and out of a cell.
This activity could be used in this unit or used as a transition to a unit on mitosis.
This activity could be used in this unit or used as a transition to a unit on mitosis.
National Standards help
Most cell functions involve chemical reactions. Food molecules taken into cells react
to provide the chemical constituents needed to synthesize other molecules. Both
breakdown and synthesis are made possible by a large set of protein catalysts, called
enzymes. The breakdown of some of the food molecules enables the cell to store
energy in specific chemicals that are used to carry out the many functions of the cell.
to provide the chemical constituents needed to synthesize other molecules. Both
breakdown and synthesis are made possible by a large set of protein catalysts, called
enzymes. The breakdown of some of the food molecules enables the cell to store
energy in specific chemicals that are used to carry out the many functions of the cell.
Teacher Information help
Potassium permanganate is not recommended for classroom use. I have used methylene blue with success.
When the students cut their potatoes in half after removal from the dye, they should see that all potatoes have about the same amount of dye.
When the students cut their potatoes in half after removal from the dye, they should see that all potatoes have about the same amount of dye.
Student Activity help
BIOLOGY LAB
SURFACE AREA AND CELL DIVISION
PURPOSE: To determine how surface area to volume ratios initiate cell division.
HYPOTHESIS: Prediction: What will happen when a dye is introduced into cubes of potatoes that vary in size? Will the dye enter the potato cube differently?
ALL STUDENTS WHO ARE IN CHARGE OF THE POTASSIUM PERMANGANATE MUST WEAR AN APRON WHILE HANDLING THE POTATOES
PROCEDURES: 1. Cut 3 cubes from a potato; one should be each of the following sizes:
0.5 cm on each side
1.5 cm on each side
2.5 cm on each side
2. Put all 3 cubes in a 5% potassium permanganate solution. Leave for 20 - 25 minutes.
3. While you are waiting, prepare a data table. Have a column each for cube size, surface area (sa), volume (v), distance of diffusion, and sa/v ratio.
4. Calculate the surface area, volume, and sa/v ratio for each cube and record on your table. We will do this step together.
A = lw (length x width) (area of one side)
SA = 6A (a cube has six sides) (total surface area)
V = lwh (length x width x height) (volume)
SA/V = SA divided by V
5. After the incubation (20 - 25 minutes) carefully remove the cubes with forceps. REMEMBER: THE PERMANGANATE WILL STAIN YOUR HANDS AND CLOTHING!
6. Slice each cube with a razor blade (CAREFUL) down the middle. Dry the razor blade before cutting each cube.
7. Measure the distance in millimeters that the solution diffused into each cube. Record the distance in your table. We will stop here for today and will finish the calculation tomorrow.
8. Calculate the sa/v ratio, record in your table and answer the following questions:
a. What happens to the surface area to volume ratio as the cube size changes?
b. As the surface area to volume ratio gets closer to 1:1, what happens to the ability of the potassium permanganate to enter the cell?
c. What would happen to a cell's ability to absorb adequate nutrients as it increased in size?
CONCLUSIONS: Use data collected in this lab to explain why cells cannot exhibit unlimited growth, but must eventually divide.
SURFACE AREA AND CELL DIVISION
PURPOSE: To determine how surface area to volume ratios initiate cell division.
HYPOTHESIS: Prediction: What will happen when a dye is introduced into cubes of potatoes that vary in size? Will the dye enter the potato cube differently?
ALL STUDENTS WHO ARE IN CHARGE OF THE POTASSIUM PERMANGANATE MUST WEAR AN APRON WHILE HANDLING THE POTATOES
PROCEDURES: 1. Cut 3 cubes from a potato; one should be each of the following sizes:
0.5 cm on each side
1.5 cm on each side
2.5 cm on each side
2. Put all 3 cubes in a 5% potassium permanganate solution. Leave for 20 - 25 minutes.
3. While you are waiting, prepare a data table. Have a column each for cube size, surface area (sa), volume (v), distance of diffusion, and sa/v ratio.
4. Calculate the surface area, volume, and sa/v ratio for each cube and record on your table. We will do this step together.
A = lw (length x width) (area of one side)
SA = 6A (a cube has six sides) (total surface area)
V = lwh (length x width x height) (volume)
SA/V = SA divided by V
5. After the incubation (20 - 25 minutes) carefully remove the cubes with forceps. REMEMBER: THE PERMANGANATE WILL STAIN YOUR HANDS AND CLOTHING!
6. Slice each cube with a razor blade (CAREFUL) down the middle. Dry the razor blade before cutting each cube.
7. Measure the distance in millimeters that the solution diffused into each cube. Record the distance in your table. We will stop here for today and will finish the calculation tomorrow.
8. Calculate the sa/v ratio, record in your table and answer the following questions:
a. What happens to the surface area to volume ratio as the cube size changes?
b. As the surface area to volume ratio gets closer to 1:1, what happens to the ability of the potassium permanganate to enter the cell?
c. What would happen to a cell's ability to absorb adequate nutrients as it increased in size?
CONCLUSIONS: Use data collected in this lab to explain why cells cannot exhibit unlimited growth, but must eventually divide.
Assessment help
NA
Enrichment / Alternative Activity help
NA
Technology Requirements/Integration help
NA