Macromolecules Lab Report PDF

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BIO-181L Cara Wright Grand Canyon University...

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BIO-181L 1 February 2021 Cara Wright

Macromolecules Lab Report Introduction Macromolecules are known to be the building blocks of life (Areda et al., 2016). The four groups of macromolecules are proteins, carbohydrates, lipids, and nucleic acids. Each test type in the Structure and Functions of Macromolecules lab tests for proteins, carbohydrates, lipids, and nucleic acids in different liquid samples. The four tests are: Benedict’s, Lugol’s Iodine Test, Biuret’s, and the Grease Spot Test. Benedict’s test is used to detect carbohydrates such as simple sugar and reducing sugars. The Benedict’s solution is mixed into a sample, which results in a color change. If there are sugars present in a sample, the test will result in a green, yellow, orange, brown or red color. If there are no sugars present, the test will result in a light blue color. Lugol’s Iodine Test is used to detect carbohydrates such as starch. Lugol’s solution has potassium iodide and it is mixed into a sample (Areda et al., 2016). If there are starches present in a sample, a dark blue or black precipitate will form. If there are no starches present, the color will remain an orange-brown because the color of the solution is an orange-yellow. Biuret’s test is used to detect amino acids such as proteins. If there are proteins present in a sample, the resulting color will be violet or lavender. If there are no proteins present, the color will remain a light blue. Lastly, the Grease Sport Test is used to detect lipids and fats. Once the samples are dry on a piece of filter paper, the water evaporates, leaving the fats and lipids to remain on the filter paper,

resulting in a grease spot (Areda et al., 2016). This means that there are fats and lipids present in the sample. If a sample does not have fats or lipids, the sample will dry from the filter paper, the water will evaporate, and there will be no grease spot. Methodology Benedict’s Test is used to detect carbohydrates that are reducing sugars. The ten samples are deionized water, glucose, corn syrup, sucrose, soda, nonfat milk, cream, unknown a, b and c. Deionized water is the negative control and glucose is the positive control and it is marked as the negative and positive controls prior to beginning the test for reducing sugars. (Areda et al., 2016). Ten test tubes are filled with the ten samples. After the samples are pipetted into the test tubes, Benedict’s solution is added into all ten of the test tubes. The test tubes are then placed into a water bath containing 100 mL of deionized water in a beaker on a hot plate. The test tubes remain in the water bath for five minutes. Lugol’s Iodine Test is used to detect starches. The samples that were used for this test were deionized water, starch, corn syrup, sucrose, potato extract, nonfat milk, cream, unknown a, unknown b, and unknown c. The two controls for this test are starch and deionized water, where starch is the positive control while deionized water is the negative control, which is marked before beginning the test. Each of the samples were placed into ten separate test tubes along with three to five drops of Lugol’s solution. If there is starch present in a sample, it will turn into a blue or black precipitate when it is mixed with Lugol’s solution because the solution contains potassium iodide and there is a reaction of amylose when the potassium iodide is mixed with a starch (Areda et al., 2016). Biuret’s Test is used to detect proteins. The samples for this test were deionized water, albumin, corn syrup, nonfat milk, cream, unknown a, unknown b, and unknown c. Albumin is

marked as the positive control and deionized water is marked as the negative control prior to beginning the test for the different samples. Each of the eight samples are put into eight separate test tubes. In addition to the samples in each test tube, the Biuret reagent is added to these test tubes. Finally, the Grease Spot Test is used to see if samples contain fats and lipids. On a piece of filter paper, eight circles were drawn. Vegetable oil was marked as the positive control and deionized water is marked as the negative control, prior to beginning the test. In each of the circle, there is one drop of each of the eight samples. The samples are set aside, and they lay on the filter paper for 30 minutes. After 30 minutes, the samples are wiped off of the filter paper, allowing the samples to dry completely, which takes about one hour (Areda et al., 2016). Data Table 1 Results for Benedict’s Test Benedict’s Test

Food Item Prediction

Conclusion Result

-

-

Li ghtbl ue

+

+

Br own

+

+

Or ange

+

-

Br own

-

+

Or ange

1 – Deionized water

2 – Glucose

3 – Corn syrup

4 – Sucrose

5 – Soda

-

+

Br own

-

+

Or ange

+

Br own

-

Li ghtbl ue

+

Br own

6 – Nonfat milk

7 – Cream

8 – Unknown A

9 – Unknown B

10 – Unknown C

Table 2 Results for Lugol’s Test Lugol’s Test Food Item

Prediction

Conclusion

Result

-

-

Cl ear

+

+

Or ange

+

-

Or ange

-

-

Br own

+

-

Br own

-

-

Or ange

-

-

Br own

+

Bl ack

+

Bl ack

1 – Deionized water

2 – Starch

3 – Corn syrup

4 – Sucrose

5 – Potato extract

6 – Nonfat milk

7 – Cream

8 – Unknown A

9 – Unknown B

-

Or ange

10 – Unknown C

Table 3 Results for Biuret Test Biuret Test Food Item

Prediction

Conclusion

Result

-

-

Li ghtbl ue

+

+

Vi ol et

-

-

Li ghtbl ue

-

+

Vi ol et

+

+

Vi ol et

-

Li ghtbl ue

-

Li ghtbl ue

+

Vi ol et

1 – Deionized water

2 – Albumin

3 – Corn syrup

4 – Nonfat milk

5 – Cream

6 – Unknown A

7 – Unknown B

8 – Unknown C

Table 4 Results Grease Spot Test

Food Item

Grease Spot Test Prediction

Conclusion Result

-

-

Nost ai n

+

+

St ai n

-

-

Nost ai n

+

+

St ai n

+

+

St ai n

+

St ai n( er r or )

+

St ai n

-

Nost ai n

1 – Deionized water

2 – Vegetable oil

3 – Soda

4 – Nonfat milk

5 – Cream

6 – Unknown A

7 – Unknown B

8 – Unknown C

Table 5 Macromolecule Tests on the Unknowns Benedict’s Test

Lugol’s Test

Biuret Test

Grease Spot Test

Possible Foods

Reveale d Food

+

+

-

+

Cr est o

Fl our

+

+

-

+

Oi l

Chi ps

-

-

+

-

Ri ceWat er

Pr ot ei n Powder

Unknown A

Unknown B

Unknown C

Analysis

Benedict’s test uses a reagent, which contains copper. The reagent is blue, and it changes color when it is heated. When heated, the reagent turns yellow to orange. The copper in the solution reacts with sugars that contain free aldehyde, CHO, or a ketone group (Areda et al., 2016). This means that the more orange or yellow, the more sugars are present. If reducing sugars are not present in a sample, the resulting color of the sample will be a light blue color. The results for each sample varied. Deionized water, sucrose, and unknown b were negative for reducing sugars because the colors of these samples were blue. Glucose, corn syrup, soda, nonfat milk, cream, unknown a and unknown c were positive for reducing sugars because the colors of these samples were either green, yellow, orange, or red. The results somewhat agree with the predictions. The prediction and the result of sucrose do not agree, which can be seen in Table 1. Since sucrose is a sugar, it was predicted that it would have a color change. However, because sucrose does not have free aldehyde, it does not react to Benedict’s reagent, which contains copper. Lugol’s Iodine Test uses a solution of iodine. This reagent reacts to a sample if there is starch present. When the reagent reacts to a sample that contains starch, the final result of the sample will be a blue or black precipitate. If starch is not present, the resulting color of the sample will be an orange-brown color. Deionized water, corn syrup, sucrose, potato extract, nonfat milk, creamer, and unknown c were negative, meaning that there is no starch present in these samples because the colors of the samples were an orange-brown. Starch, unknown a and unknown b were samples that contained starch because they turned into a blue or black precipitate. The results agree with the predictions, as seen in Table 2. Biuret’s Test uses the Biuret reagent which is a solution that is light blue in color that forms from sodium hydroxide and copper (II) sulfate (Areda et al., 2016). When a sample has

proteins present, the copper in the reagent will react with the nitrogen in the peptide bonds, which results in a color change to a violet or lavender color. If no proteins are present in a sample, then the color will remain a light blue, which comes from the reagent. As seen in Table 3, deionized water, corn syrup, unknown a, and unknown b were negative and the color of these samples were light blue, which means that there are no proteins present in the samples. The Grease Spot Test is used to detect fats and lipids. The fats and lipids in a sample will leave behind a greasy or oily-looking residue on the filter paper after the water has evaporated. The samples are placed onto a piece of filter paper and take about one hour to dry and evaporate, leaving fats and lipids behind on the paper. If there is a grease spot, that means that the sample did not evaporate completely and there are fats and lipids present in the sample. If there is no grease spot, then there are no fats or lipids present in the sample. As seen in Table 4, the results agree with the predictions, except for unknown a. The result of unknown a was that there were fats and lipids present in that sample. However, that was an error because the sample of unknown a was revealed to be flour, which can be seen in Table 5. Flour does not have any fats or lipids present. If a positive result was obtained for a negative control, a possible conclusion would be that the test was done incorrectly. Another possible conclusion could also be that a sample was contaminated or got mixed with another sample. Also, another possible conclusion could be the reagents were mixed up and confused for one another. If a negative result was obtained for positive control, a possible conclusion would be that the test was done incorrectly. Another possible conclusion would be that the sample was contaminated, or it got mixed with another sample. Also, another possible conclusion would be that the reagents got mixed up with one another or it was confused for a different reagent. The sample of Unknown A was positive for

reducing sugars, starch, and lipids. This means that the food sample would be something with corn or flour. The sample of Unknown A was revealed to be flour. The sample of Unknown B was also positive for reducing sugars, starch and lipids. This means that the food sample would be something oily or is high in grease. The food sample of Unknown B was revealed to be chips. Lastly, the sample of Unknown C was only positive for proteins and negative for reducing sugars, starch, and lipids. This means that the food could possibly be eggs, yogurt, milk, or rice water. The food sample of Unknown C was revealed to be protein powder. Conclusion This lab used four tests to detect the different macromolecules that are present in a selected group of food samples. The four tests are: Benedict’s, Lugol’s Iodine Test, Biuret’s, and the Grease Spot Test. The macromolecules being tested for are reducing sugars, starch, proteins, and fats or lipids. The different reagent from each test was used to detect the presence of these macromolecules, which are known as the building blocks of life, in different food samples (Areda et al., 2016). Benedict’s test was used to detect reducing sugars. Lugol’s Iodine Test was used to detect starch. Biuret’s test was used to detect proteins. Finally, the Grease Spot test was used to detect fats and lipids. Most of the results from the different tests support the predictions, since it was not difficult to assume the presence of the macromolecule in the given food sample. One specific error from a test was in the Grease Spot test. The food sample was the food sample of Unknown A. Unknown A was positive but it was later revealed that the food sample of Unknown A was flour, but flour does not contain any oil. The Structure and Function of Macromolecules Lab shows the presence of macromolecules in foods that are commonly purchased and consumed.

References Areda, D., Boyles, R., Francis, G., & Hite, A. (2016). Laboratory manual for General Biology I. Retrieved 1 February 2021, from http://lc.gcumedia.com/bio181l/laboratory-manualfor-general-biology-i/v1.1/#/chapter/6 Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., Jackson, R., & Campbell, N. A. (2011). Campbell Biology. Retrieved 1 February 2021, from https://viewer.gcu.edu/24WWXP...