Why Do Cells Stay Small?
The fact that you have about 100 trillion cells in your body gives us a good indication of how small most cells are. While cells come in a variety of shapes and sizes, most are extremely small. Cells are usually between 2 and 200 millionths of a meter. Fortunately, engineers are learning how to solve problems that occur with very tiny objects – including cells. The newly emerging field of Nanoengineering involves the design, creation, and control of materials or objects that are 1-100 nanometers in size. Cellular nanoengineers are working to solve a variety of problems that occur at the level of the cell.
In this exploration, student investigate the question, "Why can’t organisms be just one giant cell?” Since we don’t have the equipment needed to work at the nano-level, we will have to use a model of a cell that is large enough for us to manipulate. As our cell model, we will make three cells in the shape of a cube that are made of gelatin. The gelatin works well as a model because it allows for materials (in this case vinegar) to diffuse slowly into it. The gelatin also contains some universal indicator solution that gives the cubes a purple color. As the vinegar diffuses into the gelatin cell, it will turn from purple to red. This color change will allow you to measure how fast the diffusion occurs. It makes for an interesting exploration.
Cell Size Exploration
Cell Size Student Sheet
Cell Size Article
While this lesson is designed for 7th grade Life Science, it can easily be adapted for 5th Grade Science and High School Biology.