Macromolecules Lab Report

Introduction:
The experiment that was conducted was to identify which of the following nutrients; monosaccharides, starch, proteins, and lipids are found in the stomach contents of the four victims. The observations found will be used to validate the suspect’s claim in the murder case investigation. It is believed if the victims did actually have pancakes and eggs then the results should have a presence of starches, protein in all four contents. These results should be found because the pancake mix and egg whites contain of high protein and starch amounts.
Out of the four major macromolecules; proteins, lipids, carbohydrates and nucleic acids, only the first three macromolecules were tested for in this lab. This is because for a nutrient

investigation, nucleic acids would not affect the nutrients found in the stomach contents therefore would be of no significance in validating the suspect’s claim. Proteins are made up of amino acid chains and are essential for body functions such as: repairing cells, making new ones and growth and development of the body. Lipids are made up of hydrocarbons and form the building blocks of the structure and functions of living cells. They are used as energy sources, hormones, water proofing, insulation and cushioning. Monosaccharides are the simplest type of carbohydrates, single sugar molecule. They are usually used as energy sources. Starches are other carbohydrates made up of α-glucose and get used to convert glucose into energy that can be used.
The tests used to find the results were different for each macromolecule. For testing the monosaccharides, a water bath was heated and Benedict’s reagent was added to the four stomach content and water test tubes. The test tubes were placed in the bath and observed. Starches were tested by adding an iodine solution to the four contents and water on a spot plate. The presence of lipids were tested using two different methods, the first required a Sudan IV solution being added to the four contents and water. The second test was a translucence test, five circles were drawn on a paper towel (one for each content and one for water) and a drop of each was dropped within the respective circle. After the drops evaporated, the paper towel was held against the window to observe whether they were translucent or not. The protein test consisted of a Biuret reagent reacting with the peptide bonds – which is found in the linkage of amino acids. For all the experiments distilled water was used as a controller, since it removed any additional minerals which would have altered the results while reacting with the indicators. In addition, by using distilled water it allowed the experiment to have an example of what the reaction would look if none of the macromolecules were present. Throughout the lab, ensuring the test tubes and materials were thoroughly washed out and dried was important to minimize the risk of cross contamination between any of the contents and the indicators.

Analysis
1. If the suspect was telling the truth about all four victims eating pancakes with egg whites mixed, then the stomach contents should have shown traces of only protein and starches. This is because the egg whites contain high amounts of proteins and the pancake mix is primarily made up of starches in the form of flour. Through this investigation, the test for monosaccharides should have resulted in all the test tubes being blue because the alleged meals do not contain simple sugars. In the Sudan IV test for lipids, the stomach contents should have all stayed pink after reacting since there should not have been any lipids found from the pancakes and egg whites. Similarly, for the second lipid test, translucence test should have caused the brown paper to be opaque because there should not have been any lipids present. Since the alleged meal had proteins and starches present, the starch test should have resulted in blue-black products after the reaction took place and in the protein test, the contents should have had violet-dark purple solutions due to the peptide bond reactions.

2. From this lab, the results showed two stomach contents contained approximately 1.5-2% concentration of simple sugars because after reacting with Benedict’s reagent they turned orange. One of them stayed blue which means it had an approximate simple sugar concentration of 0%. The last stomach content turned purple-orange/brown which indicates the approximate simple sugar concentration over 2%. Based on the results of this lab, only one stomach contained lipids and the remaining had nothing or very little concentrations. This was determined based on the yellow’s darkness, in one of the test tubes, the solution turned blue-black due to the reaction with the iodine solution. The other three stayed yellow demonstrating no reaction occurred with the solution which represents the lack of presence of lipids. The lipid Sudan IV test. In the translucence test for lipid concentration, only one stomach content was translucent which means only one of the stomach contents had lipids. Finally, in the protein test the results showed one stomach contents had no protein concentration, two stomach contents had low protein concentration and one had medium protein concentration. These results were based on the reaction between the biuret reagent and peptide bonds within the proteins.
These results conclude victim one had lipids, and low concentration of proteins in their stomach, victim two had 1.5-2% simple sugar concentration, lipids (based on Sudan IV test), and low protein concentration. Victim three had 1.5-2% concentration of simple sugars, a small concentration of starches, lipids and medium protein concentration. Victim four had more than 2% of simple sugar concentration, strong presence of starches, small lipid concentration and no protein concentration.

3. No, the stomach contents would not produce the same results as in question one if they were tested an hour or two after their meal. This is because the enzymes in the pancreas would break down the starches and proteins that should have been present. (WEBISTE) When a meal is digested and sent to the pancreas, it produces enzymes such as amalyse and protease which break down starch and proteins respectively. Amalyse breaks down the starches into simple sugars, or monosaccharides which was originally not expected to be present. Protease would break down the proteins in the stomachs into amino acids therefore altering the predicted results from question one.

4. Yes, the sugars in a pixie stick would need to be broken down further to be used as an energy source because they are the disaccharide, sucrose. When sucrose is digested, the enzyme, sucrose breaks the sucrose into monosaccharides in a chemical reaction called glycolysis (HEALTHY EATING; CHEM4KIDS). The sucrose is broken down by combining with oxygen which forms usuable energy in the form of Adenosine Triposphate (ATP), carbon dioxide and water. Adenosine triphosphate is the power molecule that can be used as an energy source (CHEM4KIDS).

5. If a positive test for a macromolecule occurred in the distilled water test tube, you could conclude either the test tube was cross-contaminated or the solution was

6. The macromolecule not tested in this lab was nucleic acids. Some test methods involving this molecule is NAT (Nucleic acid testing) which tests blood donations for transfusion transmitted infections (TTIs). (JOURNAL) It involves

Discussion
In the forensic identification experiment, the results were that all the stomach contents were different and they did not have proteins and starches. The first stomach content had no sugar concentration, starches or lipids but had a small concentration of proteins. The second stomach content had medium sugar concentrations, small concentrations of proteins and no lipids or starches. The third stomach content had medium sugar concentrations as well, more starches than the previous two, strong concentration of proteins and no lipids. The fourth stomach content had a high concentration of monosaccharides, starches and medium concentration of proteins without lipids.
Through this experiment, we were able to determine whether the suspect’s statement was true.

We were able to verify the statement by finding which macromolecules were present in the stomach contents. If he was telling the truth, the stomach contents would have protein and starches in them because the egg whites and pancake mix both consist of those macromolecules respectively. To figure out the results, a series of tests were used including different reagents and indicators. For the monosaccharides test, Benedict’s reagent was used to identify when the reaction between the sugars and solution took place. The changes in colour from blue to orange-brown indicated the various approximate sugar concentrations from 0% to more than 2%. For the starch test, Lugol’s solution which is made of iodine was used to react with the starches. In the presence of starch molecules, the solution turned blue-black. In order to test for lipids, two tests were used; the first involved Sudan IV solution which can indicate lipids that are soluble in non-polar solvents. The second was a translucence test, if lipids were present in the contents, the paper would allow the light through – be translucent. Lastly, for the protein testing, Biruet reagent’s test reacting with the peptide bond allowed the proteins to be tested producing colour changes from blue to darker purple to indicate the levels of protein

concentration.
From our experiment, the results we got differed from my hypothesis. It was hypothesized that all four stomach contents would have similar protein and starch concentrations. The results however, showed different the four stomach contents were all different from each other. The first content had no colour change for the monosaccharide test (remaining blue) which indicated it had no sugars, it also tested negative for starches because when reacting with Lugol’s solution it stayed yellow indicating no reaction took place. The low protein concentration was indicated by the change in the test tube turning pink from blue due to the reaction with the peptide bonds and Biuret reagent. The lipids were present in the first stomach content because it passed both tests, it turned into a deep red with the Sudan IV solution and it became translucent. The second victim had a 1.5%-2% concentration of sugars which was seen with the reaction turning the solution orange. In the lipid test, the solution became more red with the Sudan IV test but not with the translucency test. The starch test showed a slight darkening yellow which indicated a small concentration of starches were present. The low protein concentration was determined by the change in colour from blue to pink. The third content had a 1.5% - 2% concentration of sugars similarly to the second content. It had a high concentration of proteins which was indicated with the solution turning violet from the original blue. The medium starch concentration was shown by the very slight darkened yellow and no lipids were indicated in either lipid test. The fourth stomach content only tested positive for starches because it turned into a blue-black solution from yellow. The other tests resulted in no visible change indicating a reaction did not take place. These results indicate the suspect was lying about their meals because if they had pancakes and egg whites, there should have been no traces of sugars or lipids and all stomach contents should have had the same results.
Some sources of error in this lab included weak reagents, volume measurement errors and cross contamination. The weak reagents would have altered the results by not reacting as they normally would have with the macromolecules. This could result in a false positive which would change the validity of the suspect’s claim. This source of error could be avoided by ensuring the concentrations of the reagents and indicators were strong enough to react completely with the bonds in the macromolecules. The ambiguous volume measurement from the lab of the stomach contents would alter the reactions taking place because if there is a higher amount of the contents in the test tube, the reagent may not be able to react correctly with the macromolecule, giving a faulty result. Conversely, if there is a smaller amount of the contents placed in the test tube, the reagent may react too strongly giving a false positive. Both these instances would cause false results and change the outcome of the lab which would alter the decision made about the suspect. This error could be prevented by using specific measurements for the contents in the test tubes which would allow all the tests to be measure equivalently.

Conclusion
In conclusion, the results found through this experiment tell us the suspect’s claim was not accurate therefore proving his guiltiness.