Lab Report 2 - Lab experiment to complete qualitative tests in order to discover substances’ PDF

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Lab experiment to complete qualitative tests in order to discover substances’ composition of macromolecules and use the conclusions of those tests to identify an unknown substance based on its composition....

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Biological Macromolecules Preformed- 10/14/2020 Report Date 10/16/2020

Abstract: This experiment is being performed to complete qualitative tests in order to discover substances’ composition of macromolecules and use the conclusions of those

tests to identify an unknown substance based on its composition. The experiment had several known substances (i.e. milk, dH₂ O, and Albumin) that were tested for the presence of lipids, proteins, sugars, and starch in addition to being examined for their initial appearance. The Unknown substance also underwent these same tests. After all the data was collected, the results of the known substances were compared to the Unknown’s results to correctly identify it. Introduction: The four macromolecules are carbohydrates, lipids, proteins, and nucleic acids. By understanding the general properties of these four types of macromolecules, we can learn further about the structure and function of cells. Every function that the cell carries out has its basis in the structure of these molecules. Usually, most functions of cells can be understood in terms of interactions between the molecules. For example, reproduction is quiet dependent on the properties of nucleic acids, movements, and the body’s ability to fight a disease depend on the properties of proteins. Each of the types of macromolecules is made up of subunits joined in a specific way. When many similar subunits (monomers) are joined, they become a polymer. To use macromolecules as food, we need to break them down into their subunits during the process of digestion. Our cells take the subunits and use them to build their own macromolecules During this experiment I will be testing several known substances and that will have distinguishable compositions based on their results of the presence of sugars, lipids, proteins, and starch. Then if the unknown substance undergoes the same tests it will have a similar composition through the macromolecule tests as one of the known substances. Therefore, I will be able to compare it and identify the unknown. Methods: Experiment 1: Sugar First, I measured 10mL of distilled water and mixed it with the unknown substance. Next, I separated egg whites from the yolk, and combined the whites with 0.5 mL of that with 4.5 mL of distilled water to create the albumin solution. Next, I labelled 5 test tubes with distilled water, albumin, unknown, milk, and glucose and placed 1 mL of each substance in the corresponding tube and recorded their colors. After boiling water I then placed 40 drops of Benedict’s reagent into each test tube and placed each tube into the boiling water that was in my 250 mL beaker and let rest for 5 minutes. In the end, the color would determine if there was a reducing sugar in the solution, and if so, how much. Experiment 2: Starch After cleaning the test tubes, I labeled them again with the labels: distilled water, Albumin, unknown, milk, and starch. I transferred 1 mL of each substance to the corresponding tube a put 24 drops in the case of the unknown and the starch. Then I used a white plastic spoon to scoop out a small piece of potato. Next, I used a graduated pipet to gather the IKI indicator, of which I placed one drop onto/into each substance. If the substance turned black, that would indicate a presence of starch. Experiment 3: Proteins I cleaned and labeled 4 test tubes with distilled water, Albumin, unknown and milk. I transferred 1 mL of each substance to the corresponding tube. I observed their color. Then, I added 5 drops of Biuret’s reagent into each sample and observed the color

at the time and then again after 5 minutes. If there was a purple color, that would indicate a presence of protein. Experiment 4: Lipids I put down aluminum foil on a flat surface, and then a piece of filter paper on top of it. I used a jumbo pipet to draw up Sudan III and placed one drop in 5 places around the filter paper. After that, I outlined each circle and labelled each circle with unknown, milk, albumin, distilled water, and vegetable oil. Next, I used a pipet to transfer 1 mL of each substance to their corresponding circle. I allowed the reactions to sit for 30 minutes, and if there is red coloration carried outside of the circle, that indicates that a lipid is present. Results: In experiment one it would indicate if there was a reducing sugar present in the sample. At the end of the experiment, the glucose displayed a red color, meaning the highest amount of reducing sugar was present. Distilled water was blue, as a predicted meaning it had the least amount of reducing sugar present. The milk displayed yellow, unknown displayed blue, and the Egg also displayed blue. During experiment 3 it showed if proteins were present. If the solution displayed any sort of purple color, that indicated a protein. As predicted, water displayed blue indicating there was no proteins. Since it is distilled it contains no impurities. The other solutions, Albumin, unknown, and milk, all turned purple, meaning they all contained a protein. In experiment 4 while using Sudan III, I was able to indicate which substance contained lipids. Shockingly only the canola oil showed that lipids were present. I predicted that milk would show lipids since it does contain fat. Data Table 1. Benedict’s Reagent Data. Sample

Initial Color

Final Color

dH2O

Clear/colorless

Albumin

Cloudy/colorless

Unknown

Clear/colorless

Milk

White

Glucose

Clear/colorless

Blue and Translucent Translucent blue on bottom and purple on top Translucent blue on bottom and slightly purple on top Translucent blue on bottom with white milk on top Orange

Reducing Sugar Present in Sample? Y or N N N

N

Y Y

Data Table 2. Lugol’s Iodine Data. Sample

Initial Color

Final Color

Starch Present in Sample? Y or N

Clear with a hue of red/brown.. Hue of yellow with red/brown color.

dH2O

Colorless/a bit cloudy

Albumin

Colorless

Unknown

Colorless

Clear with a hue of red/brown

N

Milk

White

White with a tint of red/brown

N

Starch

Clear/somewhat cloudy

Black

Y

Raw Potato

Cream white color with light brown skin

Black where the drop placed

Y

N N

Data Table 3. Biuret’s Reagent Data. Sample

Initial Color

Intermediate Color

dH2O Albumin Unknow n

Colorless Colorless

Light blue Light Purple

Light Blue Light Purple

Protein Present in Sample? Y or N N Y

Colorless

Light Purple

Light Purple

Y

Milk

Colorless

Light Purple

Light Purple/Cloudy

Y

Final Color

Data Table 4. Sudan III Data.

Sample

Sample Observations

Lipid Present in Sample ? Y or N

Distilled water

Red color did not move outside of circle outline

N

Albumin

Red color moved slightly outside of circle outline

Y

Unknown

Red color did not move outside of circle outline

N

Milk

Red color did not move outside of circle outline

N

Vegetable oil

Red color moved very far outside of circle outline

Discussion: Based on my results my hypothesis was supported because I was able to compare the data of the known substances to the unknow substance to identify that the unknown substance had similar composition to Albumin. Both substances tested negative for having a presence of sugar and starch but both tested positive for the presence of protein. The unknown also had a similar appearance of Albumin which also led me to thinking it was Albumin. During the experiment tests there was a substance that would test negative and one that would test positive which helped with getting a reference point of what I was looking for. The distilled water (dH20) acted as the negative since the water is distilled it does not contain impurities such as sugars, proteins, starches, and lipids. The positive control changed depending on the test. While testing with the IKI indicator the potato was the positive control and when testing with the Benedicts reagent the glucose was the positive control. By having the positive and negative controls I was able to have a better understanding of where on the spectrum the other substances were at. Overall, I feel that this experiment was successful. References: Hands-On Labs, Inc. “Biological Macromolecules Lab” www.HOLscience.com

Y...