Carbohydrates are molecules that contain Carbon, Hydrogen, and Oxygen. The most basic sugar- carbohydrate is the monosaccharide. Carbohydrate molecules are categorized by the number of carbons present in the molecule. Glucose, the most common monosaccharide has six carbons per molecule, which is called a hexose. Carbohydrates also have a 2:1 hydrogen to oxygen ratio. This aids in the condensation and hydrolysis reactions. A condensation reaction occurs when two monosaccharides join by the removal of H2O. During condensation synthesis one monosaccharide losses an OH and the other losses a H. As a result the two monosaccharides bond by forming maltose a disaccharide with a by-product of a free H2O. When three or more monosaccharides or monomer are involved in a condensation synthesis a polymer or polysaccharide is formed with a by product of water. Starch and Glycogen are two common chain polymers.
Just as the removal of water joins carbohydrates together via condensation synthesis, hydrolysis is the reaction using water to break apart Di and polysaccharide. A Di-saccharide is bound by sharing an oxygen with one hydrogen on each opposing side. When H2O is re-introduced via hydrolysis the two monomers in the disaccharide no longer need to share one H2O, and as a result the opposing sides absorb the OH and H and break apart. This reaction is a common theme in the digestion of complex carbohydrates.
Experiment 3: Test for Sugars
We will test five different solutions for presence or absence of reducing sugars using a premixed Benedict’s reagent. These dependent variable solutions will be water, glucose , onion juice, potato juice, and starch suspension. When the Benidict’s reagent is combined with sugars at a boiling temperature, a color reaction will occur. Our independent variable, Benidict’s reagent color is blue.
The negative control will be the combination of water and Benidict’s reagent. This sample will undergo all the steps of the test except for the one being tested for i.e. sugars. If the end result is negative color change (blue) , it will thus be determined that the experiment and the Benidict’s reagent is not contaminated and the experiment may proceed. The negative control will also serve as a comparison to gauge against the color change in the other four sugar tests.
EXPERIMENT 3: Test for Sugars: TESTS MAT. ; METHODS HYPOTHESIS RESULTS
Tube 1 1cm water+2cm Benidict’s reagent. No color change
Negative control no color change. Neg-sugar. Blue
Tube 2 1cm glucose solution+ 2cm Benidict’s reagent. Boil 5-10 min. Color change due to sugars. Orange+red color, Pos-sugars.
Tube 3 4 drops onion juice+ Fill to 1cm mark water +Fill to 3cm mark Benidict’s reagent. Boil 5-10 min. Color change due to sugars Yellow+orange
Tube 4 4 drops potato juice+ fill to 1cm mark water +Fill to 3cm mark Benidict’s reagent. Boil 5-10 min. Color change due to sugars. Green+blue
Tube 5 1cm starch suspension+ Fill to 3cm mark Benidict’s reagent. Boil 5-10 min. No color change
due to no simple sugars. No color change Neg-sugar
Tube contained water and Benidict’s reagent. This experiment was our negative control. Since negative results where acquired we could conclude that our reagent was not contaminated and the experiment could continue. Tube 2 contained glucose. Glucose is a monosaccharide or simple sugar which gave the most color change. Tube 3- onion juice contains both mono and disaccharides , which caused a moderate reaction. Tube 4 contained potato juice which contains very little simple sugars resulting in a mild reaction. Lastly tube 5 contained starch suspension which consists of polysaccharide and no simple sugars, thus no reaction occurred.
Experiment 4: Iodine Test for Starch
When Polysaccharide or starch units are placed in the presence Iodine a reaction occurs. Iodine (brownish in color) will be absorbed by the starch units to form a blue black color.
In this experiment we will test 2 solutions and 2 substances for the presence of starch. Iodine will be the independent variable. Our dependent variable will be water, starch suspension, potato piece, and onion piece.
Our negative control will be the combination of water and iodine. This sample will undergo all the steps of the test except for the one being tested for i.e. starch. If the end result is negative color change (brownish) , it will thus be determined that the experiment and the Iodine is