Macromolecule Lab Reflection

A couple of days ago in class we performed a lab on macromolecules. In the lab we got either an egg white, an egg yolk, a potato, an apple, an onion, a lemon, or a strawberry. My partner Mayze and I were given the potato. First as a class we conducted tests on substances we knew to contain either protein, glucose, starch, or lipids. First we tested gelatin by adding 10 drops of Biuret solution to it. The result was that it turned a brownish, carmel color; indicating it contained protein. Next we tested pure glucose, by adding 3 mL's of Benedict's solution and adding it to a beaker of boiling water. The glucose changed from blue, to green, to a layer of colors. Next we conducted a starch test on starch, by adding 5 drops of Lugol iodine solution. The starched turned a dark black. Last but not least we conducted a lipid test on cream cheese by rubbing it on brown paper. After letting it dry there was a visible shiny/glossy fat. After performing the four tests we broke off into our small groups. Mayze and I began by cutting up the red potato into small bits. First we put some into three test tubes, and began performing the various tests. When we added 10 drops of Biuret solution to one test tube. We could see no visible change, and determined that there was no protein in potatoes. Next when we added 3 mL's of Benedict's solution a different test tube and put it into boiling beaker of water. Almost immediately it changed to a yellowish-orange, so we knew it contained Glucose. After that we added 5 drops of Lugol iodine solution to another test tube of potatoes they began to turn black so we determined that the potato contained starch. Finally we used the brown paper we cut the potatoes on and hung it up to dry overnight. The next class we looked at it, and determined that there was no lipids in the potato.