Organic Chemistry Lab

ORGANIC CHEMISTRY LAB REPORT

Testing For Biological Macromolecules

Presence of Proteins, Lipids, and Carbohydrates in Organic Matter

AP Biology, Mod 19

Abstract

The testing of the presence of sugars, lipids and proteins was accomplished through the procedure provided by Mrs. Wooton.  We observed the presence of these essential compounds through the use of the indicators starch solution, benedict's solution, and NAOH. In the test, all of the controls (test tubes filled with water/water solution) remained the same, and the test tubes with the indicators a part of the solution showed as much. The solutions with the indicators did as the procedure stated. The data shows that these essential compounds are identifiable in nature.

Introduction

In this lab, we explore 3 organic compounds: carbohydrates, lipids, and proteins. Carbohydrates include the sugars and their monomers are called monosaccharides and include glucose, fructose, and galactose.  Lipids are used for energy storage in organisms and also provide protection and insulation, they also carry chemical messages and are important in building blocks. Proteins are made up of monomers called amino acids and there are 20 amino acids in organisms.

These compounds are important and necessary for life because Organisms use these compounds in the process metabolism to synthesize structures such as muscle tissue and also to break down substances such as digesting food for energy. As human organisms you can see how lipids, proteins, and carbohydrates are very important and vital to our body.

              The main objective of this lab was to figure out what type of reactions would the organic compounds starch, protein, and lipids when we add 5 drops of Benedict's solution. The organic compounds are made up of simple structures, monomers, and can build more complex molecules, polymers. We were looking for a positive test reaction to the organic compounds when we added 5 drops of Benedict’s solution. The purpose of this lab was to learn about Organic Compounds. We wanted to know what would happen when we test certain organic compounds such as starch, proteins, and lipids.

       We hypothesized that the essential compounds would test positive because the resource in which we received the procedure was reliable, and it told us that the compounds would. We knew that we would follow the procedure, and make sure to do exactly what it asked, to assure that the results would be as described. The source was reliable, because our dear Biology Facilitator would never do anything to lead us astray.

Methods

Simple sugar test:

1.      Using 2 marked test tubes, put 5 drops of water into one and 5 drops of glucose into the other.  Add 5 drops of Benedict’s solution to each.

a.     What is the initial color in each tube?

2.     Heat the tubes by placing them in a boiling water bath.  Observe any color changes that occur. *A positive test for simple sugars is orange.

a.     Did a color change occur in either tube?

b.     If so, which one?  Explain.

Starch test:

1.     Using 2 marked test tubes, put 5 drops of water into one and 5 drops of starch solution into the other.

2.     Place 1 drop of iodine into each tube. *A positive test is dark blue or black.

a.     Did a color change occur in either tube?

b.     If so, which one? Explain.

Protein test:

1.      Using 2 marked test tubes, put 10 drops of water into one and ten drops of gelatin into the other.

2.     Place 3 drops of CuSO4 into both.

3.     Place 10 drops of NAOH into both. * A positive test is turquoise or purple.

a.     Did a color change occur in either tube?

b.     If so, which one? Explain.

Lipid test:

1.      Spread 2 drops of oil on a piece of brown paper.

2.     Place 2 drops of water beside these. *A positive test is a translucent spot.

a.     Did either sample test positive for oil?

b.     If so, which one? Explain.

Results

Test Tube/Paper Towel Observations

Test for:	Initial observation: constant	Initial observation: variable	Final observation: constant	Final observation: variable
Starch	clear water	foggy white	clear with tint of brown (iodine)	deep purple
Sugar	light blue	light blue	light blue	orange
Protein: Biruret test	very light blue	very light blue	very light blue	dark blue/purple
Lipid	wet paper towel	wet paper towel	dry paper towel	greased paper tower

Biruret Test final observations               Sugar Test final observations

Starch Test final observations        Lipid Test final observations

Discussion

In this experiment, we observed the presence of each biological macromolecule in the corresponding test. In every test, the constant (water) proved the absence of the macromolecule being tested by an observation that a chemical reaction did not occur. In the test for starch, the starch solution with the addition of iodine observably changed from a foggy white liquid to a deep purple indicating the presence of starch. In the sugar test, the the glucose solution with added Benedict's solution visibly changed from a light blue to a solid orange color after added heat, indicating the presence of simple sugars. In the Biruret Protein test, the gelatin with added CuSO4 and NAOH changed from a light blue to a dark blue/purple indicating the presence of protein. In the Lipid Test, the observation of a greasy, translucent spot where the we can tell a lipid was present (the constant evaporated leaving a dry spot).

Conclusion

The purpose of this lab was to test for the presence of 3 of the 4 essential compounds: lipids, proteins, and carbohydrates. Following the procedure provided, we were able to find the presence of these compounds. For example, when we heated the solution of water, gelatin, CuSO4, and NAOH, it turned a very vibrant orange, from its original blue. This proved the presence of protein in the gelatin. The presence of these compounds is testable.