A Blood Bag With Two Pipettefuls Of Glucose And Starch Solution

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In part I, a dialysis bag with two pipettefuls of glucose and starch solution was mixed. The bag was placed in a beaker of tap water and I2KI solution for 30 minutes. The contents of the bag and the beaker were placed in test tubes and tested through Benedict’s Test for the presence of aldoses - both test tubes tested positive. What was happening when the dialysis bag was in the beaker? The dialysis bag’s material acted as an artificial “membrane”, exercising selective permeability (allowing certain membranes to pass in and out of the bag). Originally, the bag contained starch and glucose, whereas the beaker contained water and I2KI solution (starch indicator). The concentration of glucose was higher in the bag than outside the bag, thus…show more content…
I2KI’s concentration was higher outside the bag than in the bag, so I2KI diffused down its concentration gradient, from an area of greater I2KI concentration to an area of “lower” I2KI concentration. This is shown through the color of the dialysis bag after being placed in the beaker for 30 minutes. Originally, the dialysis bag with glucose and starch was a clear color, but when the I2KI solution diffused into the bag, the solution turned black because I2KI turns a solution black when the presence of starch is detected. In part II of the lab, potato slices (of approximately the same mass) were placed in cups of varying sucrose concentrations. All seven cups contained approximately 50 mL of sucrose (0.0M to 0.6M, in 0.1M increments). After the potato slices were incubated for about 24 hours, they were removed, blotted dry, and weighed. A graph was created by the effect of sucrose concentration on the percentage change of mass of the potato slices. The graph/data shows that as the concentration of sucrose increases, the percentage of change of mass decreases - an inverse relationship. For example, when the potato slices were placed in the 0.0M sucrose solution (pure water), the change in percentage mass was 29.94%; the mass increased by 0.53 grams. The solution was pure water, thus a higher concentration of
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