5. Slimy cells - Lesson Plan
- Begin class with a review of the parts of the cell.
- Describe the activity to students – they will be making 3 dimensional cell models. A ziplock bag will represent the cell membrane. Slime will represent the cytoplasm. If they wish to make a plant cell, strawberry baskets will represent the cell walls. Students can choose the rest of the “parts” to make up all the organelles.
- Discuss as much of the chemistry behind the making of slime as you wish.
- Pass out the slime making materials and lead students through the creation of slime.
- First, each student will need a ziplock bag.
- Using the graduated cylinders, measure out 180 ml PVA and add that to the bag.
- Using the small beakers, measure out 30-35 ml colored Borax – mix and match colors as you wish to get the final color you want – and add that to the bag.
- Zip the bag closed and gently massage the contents until the colored Borax is evenly distributed throughout the PVA and the slime coalesces.
- The slime may now be touched and/or carefully taken out of the bag.
- Pass out the handout and describe the assignment – in addition to adding organelles to the cell, students should create a key describing what was to represent each part of the cell and why that object was chosen. (Is it similar in size? shape? function? design?)
- Answer any questions. Have students set up the key on a piece of paper before they go to the cell parts “buffet” (or else some may never get around to creating a key at all or understanding the purpose of the activity).
- Once students have their key outlined and decided whether to make an animal or plant cell, allow them to browse the cell parts “buffet” and add objects to their cell. Make sure that they record what they chose for each organelle and why on their key.
- When all the cells are complete, go through each part of the cell and survey what different students chose to represent that part and why. This helps reinforce the vocabulary and the functions of each organelle.
- Ask students how many times larger this ziplock bag cell is compared to the cheek cells they observed under the microscope. (Almost 3,000 times larger!)
- To show students how this is calculated, present and describe the metric system of measurement.
- A ziplock bag is around 16 centimeters wide. A centimeter is one hundreth of a meter (0.01 meters). This a ziplock bag is 0.16 meters wide.
- A cheek cell is 58 micrometers wide. A micrometer is one millionth of a meter (0.000001 meters). Thus, the cheek cell is 0.000058 meters wide.
- To see how much larger a ziplock bag is compared to a cheek cell, divide the size of a ziplock bag (in meters) by the size of a cheek cell (in meters): 0.16 m/0.000058 m = 2,759
- Since all living things are made of cells, how tall would a person made of ziplock bag sized cells be? A typical middle school student is around 1.6 meters tall. To calculate this, you need to set up a ratio:
__x__ = __0.16 m__
1.6 m 0.000058 m
Solving this ratio, you find that x is 4414 meters (4.4 kilometers or 2.7 miles)! Thus a person made of ziplock bag sized cells would be 2.7 miles tall! See some of the other fun facts in the teacher background.