Experimental Sciences

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The “Visking” Tubing Experiment

The human body is a complex system that consists of varying organ structures working and indefatigably functioning in sync together to maintain equilibrium, thus, to sustain life.

IB DP Year 2 students took their first on-hand experiment on digestion, called “Visking Tubing Experiment”. One of the best ways to learn and understand the processes that take place in the body is by modelling. This experiment provides a visual way of demonstrating diffusion through a semi-permeable membrane. It was used to model the human gut as well as to investigate the effect of the enzyme called amylase on starch. Two standard macro molecules tests were done. The first test done is called the Iodine Test. It is done to determine the presence of starch in certain foods or substance. The second test done was the Benedict’s test, which is used to test for the presence of reducing sugars, such as glucose.

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The Visking Tubing Experiment set-up

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Benedict’s solution, used to test for the reducing or simple sugars.

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All samples were taken and were submerged in hot water bath. Benedict’s reagent starts out aqua-blue in color. As it is heated in the presence of reducing sugars, it turns yellow, green, orange or brick-red. The final color of the reagent signifies the concentration of reducing sugar. Brick red signifies a high concentration of glucose.

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Iodine solution

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Iodine solution, used to test for starch. A blue-black color results if starch is present. Otherwise, the original brown color will will be retained.

  • http://www.deped.gov.ph/