Day 5 -- Back to Square One

We continued the experiment today. It's very odd to finish parts 2-4 before finishing part 1 or 5, even more to add in a sixth and seventh step. There's probably a plausible reason for the skipping around. 

This dialysis tubing contained a solution of 15% Glucose and 15% Starch. After adding 8mL to the tube, we tested it with a Glucose Strip. (There was not much to expect: it detected glucose.) We then tested the 50mL of water with the same glucose strip and, receiving a negative response, continued with the experiment. 

Then there was some confusion. Mr. Quick had apparently told us to add the 1mL of iodine after waiting 15 minutes. However, the instructions instructed us to add it immediately. It is doubtful that this mistake negatively affected the results, but it is a notable step.

The cubes of KI sitting around. The color went from white
to black rather quickly.

While that sat around, we started the second part. Daniel and I were given a block of Potassium Iodide (KI). We measured the surface area and volume of the cubes and placed it in an indicator. The brownish-red liquid seeped into the sides of the KI, simulating a cell's diffusion of substances through the cell wall. Different sized slices of the KI required a different amount of indicator. When they were removed, we observed the distance that the indicator had leaked into the "walls" of the cube. 

We mercilessly sliced the cubes lengthwise, revealing the layer of black that had seeped through. That black was measured and calculated, based on the size of the cubes originally. 

KI cube 2, after being sliced

The cubes were representative of cells, the experiment showing the effects of surrounding liquids on a cell wall and the wall's reactions.

Removing the solution of Glucose and Starch from its watery prison, we placed a few drops of the surrounding water in an indicator. It positively detected glucose in the surrounding water. Why is this? Because the membrane of the dialysis tubing is semi-permeable, it allows the smaller glucose molecules to pass freely through, while disallowing the larger starch molecules any access to the outside.

More information soon...