Macromolecules: Proteins and Carbohydrates

Introduction

The purposes for the experiments were to detect if the substances would test positive for the following: Protein, Starch and Sugar. Proteins are made up of amino acids and have various functions such as transportation, regulation and chemical breakdown. Starch is a polysaccharide made of many glucose units. Plants store glucose as starch for energy storage. Glucose is used as ready energy and made of one sugar molecule which is a major source of cellular fuel for all living things (Mader, 2010). The hypotheses for the protein experiment were: albumin will test positive for proteins because proteins are in blood. Pepsin will also test positive for protein because it is an enzyme that digest protein (pepsin, 2012). Starch will not test positive for protein because it is a starch. The second experiment for starch the hypotheses were: the starch suspension will test positive for starch because it is a starch. Onion will also test positive for starch because it is a type of plant and plants store starch. The potato will test positive for starch because it is a polysaccharide and glucose will not test positive because it is a monosaccharide. For the last experiment on glucose the hypotheses were: the glucose solution will test positive for glucose because it is glucose. Starch will not test positive because it is a polysaccharide. Onion will test positive for glucose because it contains simple sugars and for potato it will test negative for glucose because it contains starch which is a polysaccharide.

Materials and Methods

The materials needed were nine test tubes, one beaker, heating plate, ruler, droppers, gloves and a wax pencil. The substances used were distilled water as the control, albumin, pepsin, starch, biuret’s solution, starch suspension, onion juice, potato juice, glucose solution, iodine and benedict’s reagent.
The first experiment was performed to analysis if the substances: albumin, pepsin, and starch would test positive for proteins. The test tubes were marked at the 1cm level using the ruler. Test tube one was filled with water (control) to the 1cm mark then five drops of biuret’s reagent was added. The tube was covered with a gloved thumb and swirled to mix carefully. The steps were repeated with the albumin, pepsin and starch.
The second experiment was performed to analysis if the substances: starch suspension, onion juice, potato juice, and glucose solution would test positive for any starch. Each test tube was filled with one of the substances to the 1cm mark and five drops of iodine were added.
The third experiment was performed to check if any of the substances: glucose solution, starch suspension, onion juice, and potato juice would test positive for glucose. Each test tube was filled with one of the substances to the 1cm mark then five drops of benedict’s reagent was added. The test tubes were then placed into a boiling beaker for 5 minutes.

Results

Experiment one: if any proteins were in the substances they would turn purple once the biuret’s reagent was added. Albumin and pepsin turned purple and tested positive for proteins. Starch stayed blue and tested negative for proteins. See Table 1.1 Tests for Proteins.
Experiment two: if any of the substances turned black once the iodine was added it would have starch in it. The starch suspension and potato juice tested positive for starch and turned black once the iodine was added. The onion and glucose solution turned an amber color and tested negative for starch. See Table 1.2 Tests for Starch.
Experiment three: If any of the substances were positive for glucose after the benedict’s reagent was added and they were boiled they would vary in color from low concentration green/yellow to a high concentration orange/red. Glucose solution turned orange for a high concentration and tested positive for glucose. The onion juice turned orange-red for a very high concentration and tested