Diffusion Lab Essay (also on Google Docs)

Like every lab, this one had a point to prove. We diluted the iodine and starch separately using osmosis, and watched as the iodine diffused into the plastic baggie with the starch solution. Since iodine is an indicator, it became purple as a reaction to the contact with the starch. At the beginning, the iodine was hypertonic in the beaker and the starch in the bag. After sitting for a while, the iodine became isotonic in the beaker and the bag, after half of it had penetrated the selectively permeable membrane of the bag. The Starch remained hypertonic in the bag and hypotonic in the beaker. The reaction was not as great as it would have been had it been pure iodine and starch, but it wasn’t as concentrated so it took longer.

This experiment is like the cell membrane of a plant or animal cell. The cell’s selectively permeable membrane allows only certain things in and out of the cell. It needs to bring in nutrients, while keeping out materials that can harm the cell, and it must allow waste products out, while keeping the organelles inside of it. Just like the bag was letting the iodine molecules out, while keeping the water out and starch in it. The iodine molecules were small enough to go through the selectively permeable membrane, while the starch and water molecules were not. That basically the main idea that this experiment proved.

What does this have to do with life? Besides being the way that cell the membrane in the cells, which happen to make up everything, work, this experiment can relate to life in many ways. For example, a screen door. A screen door is very simple. A wire mesh that lets air in, air out and makes sure that bugs don’t come in at all. Like the iodine and the baggie, air molecules are small enough to get in, but bugs are not. An example of another indicator is baking soda. When it comes in contact with vinegar it foams up and produces gas. When it comes in contact with lemon it has the same reaction. We use osmosis every time we drink powdered Kool-Aid, diluting the red powder in the water. There can be high or low concentration of people in a room, or a low concentration.  An object can be hypertonic, hypotonic, or isotonic in an area. This experiment was very useful for learning about life. I hope we do more labs like this in the future!