Macromolecules Lab Reflection

     Yesterday during biology class we conducted a series of lab tests to find what macromolecules existed in different foods. Each lab partners were given either egg whites, egg yolks, potatoes, apples, onions, strawberries, or lemons, and were required to find if those foods contained protein, glucose, starch, and/or lipids.  We used different indicator tests to look for each macromolecule.  (shown in picutre) Some of the results were very unexpected and interesting.

     My lab partner was Shelby and we were assigned strawberry. (shown in picture) My prediction was that strawberry would contain glucose, but no protein, starch, or lipids. We tested for glucose by adding 3 mL of Benedict's solution to 5 mL of strawberry in a test tube, then we put the test tube in a beaker of boiling water and heated it. The pink/red strawberry changed to a bright orange color after five minutes. The color change indicated that the strawberry contained glucose. To test for starch, we added five drops of Lugol's iodine solution to 5 mL of strawberry. The strawberry did not turn black, and this meant that there was no starch in the strawberry. We tested for proteins by adding ten drops of Biuret solution to 5 mL of strawberry, and the pink/red strawberry changed to a brown color. This showed that the strawberry had proteins. For the final test, we rubbed strawberry on to a piece of brown paper to look for lipids. We let the paper dry over night, and no glossy finish or grease on the paper was visible, which meant that there were no lipids in strawberries.

     It was very interesting to see the other groups results. For example, I was surprised to see that lemon contained none of the four macromolecules we tested for. I was also surprised to see that the egg yolk and the egg whites didn't have protein in them but strawberry did.  However, experimental error could have occurred because the group could have had a problem, so its possible that the results aren't entirely accurate.  From this experiment I learned a lot about the different macromolecules that exists in different foods.  It was very interesting and fun.

 Picture #1 from: (http://media.photobucket.com/image/starch,%20glucose,%20lipids,%20proteins/veewhy_x3/Sept07/0919075.jpg)
Picture #2 from:
(http://art4linux.org/system/files/strawberry.jpg)