Dyalisis Diffusion

The purpose of this lab was to recreate and observe diffusion using goat intestin...*ahem* dialysis tubing and the substances that move in and out of the membrane of the cell . We filled a dialysis tube with a starch solution and dunked it into a solution that we dyed orange.

We redid this whole experiment with glucose instead of starch. After 20 minutes, we pulled the first dialysis tube out of the colored water and saw that the color of the startch solution in the tube had changed to blueish black color. Then we dipped an rapidly inflating(5000x inflation) glucose test strip that Mr. Wong bought for 10/3 of a dollar for each strip into the glucose solution beaker and discovered that it had changed to a different color than before.

We used two beakers, iodine and dropping pipette, dialysis tubing, Glucose test strips, distilled water, a starch solution, and a glucose solution.

Twist one end of a piece of dialysis tubing. Fold the twisted end over, and tie it tightly with a piece of string. Prepare the other piece the same way.

Pour soluble -starch solution to within 4 cm the top of one piece of tubing. Twist and tie the end as in step 1. Rinse the tubing under running water to remove any starch fro the outside. 

Place the tubing in a cup of water labeled A. Pour enough Lugol’s iodine solution to give the water a distinct yellowish color. 

Repeat step 2 with the second piece of dialysis tubing, using glucose solution instead of the soluble starch. Place this tubing in a beaker of water labeled B.

Allow the pieces of tubing to stand for about 20 minutes. Dip a glucose test strip into the water in beaker B. Record the color on the strip.

Observe the tubing in beakerA. Record any changes, including color, that you see in either the tubing or the water in the beaker.

Let beakers A and B stand overnight.Record any changes observed the next day. 

In the starch experiment, the iodine molecules from the in beaker A moved to the starch solution inside, turning the starch solution blue. This is because of osmosis, which allows it to travel from greater concentration to smaller concentration. In the glucose experiment, the glucose molecules moved from the inside to the outside as we tested using the glucose test strip that proved that the concentration outside was greater than before. We did not stay overnight and therefore, I cannot answer analysis 3. The starch molecules couldn't pass through because it was too large. If the iodine molecules are small, and the glucose molecules are smaller than starch, both of these molecules would have been able to diffuse. The structure probably contains pores which allow for the diffusion.

In conclusion, I learned that membranes are very complex structures and they can let small molecules like water and iodine in and also,glucose but not big molecules like starch.