Pre-Lab: Identifying Carbohydrates

Pre-lab 1: Identifying Carbohydrates
Abstract
The point of this lab is to determine if a substance contains carbohydrates such as a reducing sugar and/or polysaccharides. This will be done by using Benedict’s reagent and Iodine stain tests. Benedict’s reagent will react to reducing substances in the solution by oxidizing it and changing the structure of the reducing sugar to form a colored precipitate. The color of this precipitate can be used to determine the concentration of reducing sugars in the substance. If the precipitate is blue no reducing sugars are in the substance. If the precipitate is bluish green, green, yellow, or orange it does contain reducing sugars. Iodine stain will be used to determine if the solution contains polysaccharides.
If the product is yellow no polysaccharides are in the substance. If the substance is bluish black, dark reddish brown, or violet brown the substance does contain polysaccharides.
Background
A carbohydrate is an organic compound that is made up of oxygen carbon and hydrogen and includes both sugars and polymers of sugars. Carbohydrates are different from other organic compounds because it goes by the empirical formula of Cm(H2O)n and has a hydrogen to oxygen ratio of 2:1. There are three types of carbohydrates, the first being monosaccharides, which are simple sugars such as fructose and glucose. One of their main purposes is to act as an energy source for plants and animals; such as glucose being broken down during cell respiration. Monosaccharides are also monomers which serve as building blocks for more complex carbohydrates to form. Disaccharides is the second group and consists of two monosaccharides joined together by glycosidic linkage. They are common components found in what people eat and mainly serve to give nutrition to said diets. The third group is polysaccharides, the polymers of carbohydrates, which are made up of a few hundred to a few thousand monosaccharides. This
Be sure that the water does not boil too strongly and if it does occur reduce the heat. Put 12 test tubes on the test tube rack and label them 1 through 12 on the top of the tube using wax pencils. Use the ruler to draw a line at 3 cm and 6 cm on the test tubes using the wax pencil. Fill the test tube up to the 3 cm line with the solution to be tested and fill up to the 6 cm line with Benedict’s reagent. Invert test tubes to mix the liquid. Place the test tube in the hot water bath for 3 minutes and remove with test tube holder. Observe the results and record the data in table 4 then repeat all steps with the remaining 11 test tubes and substances. Once finished dispose of all solutions in hazard container and clean the test tubes with soap and water.
For the iodine test get 12 test tubes and place them in a test tube rack, then label them 1 through 12 using a wax pencil. Using a ruler measure out 3 cm on the test tube and draw a line, this line will represent 3ml. Fill the test tube to the 3 cm line with the test solution and add 3 drops of iodine stain. Invert test tube to mix substances and observe the results and record them in table 4. Repeat these steps for the remaining test substances. Dispose of all solutions in hazard containers then clean the test tubes with soap and