Diffusion and Osmosis Lab Part 1

Here is Part 1 to my lab. The lab demonstrates how diffusion and osmosis work which is slowly helping us learn about the cell membrane. In this lab my group and I needed water, starch, glucose, iodine, dialysis bag,plastic cup, and glucose indicator strip. The first step that we did was fill the plastic cup with 2/3 of the way with water and put approximately 4mL of iodine. The results of those two mixed together was the water became brown, which is the color of the iodine. We then stuck a glucose indicator strip in the water and got the results of negative presence of glucose. Next we tied the bottom half of the dialysis bag off with string and filled the dialysis bag with 15% glucose and 1% starch. We tested the solution with a glucose indicator strip and it was positive for the presence of glucose. After testing the solution in the bag I tied off the top of the bag that way no solution entered or exited. We observed the color of the solution in the bag and it was a white foggy color.

We then immersed the bag that contained 15% glucose and 1% starch into the cup that contained water and iodine. Now that the experiment is set up, we let it sit for 24 hours/until the next day in class.

When class started the following day, we pulled the bag out of the cup and observed the color change. We also observed the color change in the cup. The color of the solution in the bag was clear with a dark purple/blackish spot at the bottom. We moved the bag around which caused the colors to merge to make sure the color of the spot was correct. The color of the solution in the cup turned into a deep yellow color. The next step in this experiment was to test the solution in both inside the cup and inside the bag with the glucose indicator strip. They both tested positive. If you have no clue what diffusion and osmosis means, than you are probably lost. Well diffusion means when the movement of particles from areas of high concentration to areas of low concentration. For example, when you spray perfume or febreeze it will spread from a high concentration to a lower concentration. Osmosis is the movement of water into and/or out of the dialysis bag "cell". The water goes from a high concentration to a low concentration and does so over a membrane.

Now that the experiment is done we can come to a conclusion to what has happened. There is a substance that is leaving the bag and that substance is glucose. The starch stayed in the bag because it is a polysaccharides, which means it is a chain of monosaccharide's linking making it to big to pass through the bag "cell membrane". Glucose passed through because it is a monosaccharide, which means it is small enough to pass through the cell membrane. We have evidence that glucose passed through the bag "cell membrane" because we tested the cup and the bag both with glucose indicator strips. The bag and the cup both tested positive for glucose. More evidence I have proof for is that water entered the cell membrane because the bag "cell membrane" increased in size. Here is a fun fact, when you go to the hospital and you are dehydrated, they give you an IV but the fluid they are giving you is not pure water because if it was your cells would explode since they expand when a lot of water enter them. In the IV bags they have saline which helps have equal amount of salt and water. If you still are having trouble understanding check out part 2 for this experiment please.