Macromolecules Lab Report

Benedict, Biuret, Iodine and brown paper bag tests were conducted in order to identify various macromolecules which might be present in the two unknown substances given. Qualitative data was gathered on the bases of clarity, viscosity, odor, state of matter and most importantly color change. The data gathered was then complied in table two of this lab.
Table 2 represents the data compiled for unknown substances #6 and #7. When substance #6 was tested for the presence of protein, it did change color from blue to yellow, however this color change indicated a negative result. According to the results gathered in Table one, Part one of this lab, a color change from blue to light purple indicates a positive result; not blue to yellow. When Iodine

solution was added to the substance no apparent visual changes were observed. Likewise, when tested for the presence of lipids, the brown paper bag got wet however was not transparent, thus indicating a negative result. Therefore starches, proteins and lipids were not present in this particular substance. Conversely, when Biuret solution was added to the substance, its color changed from blue to brick red and left a precipitate at the bottom of the test tube when heated in the hot water bath. The positive test indicated that glucose was present in this substance.
As previously discussed in the introduction, carbohydrates which can be oxidized by copper ions are referred to as Reducing Sugars (Christensen, T. E., 2014, August 26).When a solution (similar to substance #6) containing Benedict’s reagent and a reducing sugar are heated, the copper sulfate present in the Benedict’s solution is reduced to copper (I) oxide. Due to the oxidization of copper sulfate the solution changes color from the initial blue to green, orange, red-orange or brick-red depending upon the quantity of reducing sugar (Simoni, R. D., Hill, R. L., & Vaughan, M.,2014).
The same Benedict’s tests can be used to identify macromolecules present in foods containing high concentration on glucose, fructose, maltose etc. Examples of such would be maple syrup and most fruits and juices (Ganong, B., 2007, June 14). Benedict’s test is not only useful for identifying macromolecules in foods it could also be used to test urine samples for the presence of glucose in patients who ae suspected of having diabetes (Christensen, T. E., 2014, August 26).
The lab was successful in accomplishing its purpose; however there are several sources of errors inherent in the experimental procedure which may have screwed the results gathered. The first and most obvious is the observer’s subjectivity. No two people see exactly the same colors. What may appear purple to one might not appear purple to others. The second source of error could be limitations of the reagents used themselves. As an example, Benedict’s test cannot be used for all sugars as it only reacts with reducing sugars. Sucrose, a non-reducing sugar, contains fructose and glucose which are joined by their glycosidic bond in such a way as to prevent the glucose isomerizing to aldehyde, or the fructose to alpha-hydroxyl-ketone form (Christensen, T. E., 2014, August 26)