Investigation of Living Things: Lab Reflection

         In the Investigation of Living Things lab, we took different foods (Egg whites, egg yolks, apples, onions, potatoes, lemons, and strawberries), and did different tests to each of them which identified if the food had protein, starch, glucose, or lipids, depending on the test. In the test for protein we added 10 drops of a solution that identifies protein in substances called Biuret solution, to 5mL of the food and waited to see if the test was positive of negative. The Biuret solution itself is blue, but after a while, a caramel-brown color should appear on the sides of the test tube if the food contains protein. If nothing happens then that food does not have protein. In the glucose test we added 3mL of Benedict's solution to 5mL of the food, and then heated the test tube that they were in for 5 minutes. If the test was positive, the color in the test tube should have changed dramatically, into a sort of cool orange/red/yellow color. In the starch test we added 5 drops of Lugol's iodine solution to 5mL of the food, and if it tested positive then the color in the test tube should have turned a dark black. And lastly, in the test for lipids we smeared some of the food onto a piece of brown paper, let it dry over night, and then observed the piece of paper the next day. If the test was positive, when held up to light a glossy cover should be visible where the food was smeared.

         I thought that this was a cool lab because it applied what we had learned about macromolecules to foods that we eat on a daily basis. I had always just thought that an apple was an apple, and that was it, but after doing this lab i realize that an apple contains glucose and starch, and is made up of millions of microscopic cells all bonded together. I think it was a fun and active way to put what we had learned in chapter one in perspective, and to really put the idea in our heads that everything in the world is made up of cells, which are made up of many different atoms, elements, molecules, and macromolecules which we have just started learning about.