Identifying Macromolecules in Solutions

Identifying Macromolecules in Solutions

David Bajic, 20571847

Amandeep Pabla

Maple Ong and Sally Choo, Section 018

BIOL 130L – 018, Tuesday, (2:30-5:20), Biology 2 151

September 22nd 2015

Introduction:

        As the name would suggest, a macromolecule are molecules with great size, which ultimately makes up more than 90% of the cells entire mass. Macromolecules are commonly created by polymerization of much smaller subunits called monomers. The four major building blocks of macromolecules include; carbohydrates, lipids, nucleic acids and lastly proteins (Karp Gerald 2013). Carbohydrates consist of polymers of a simple sugar molecule called monosaccharides. With that being said, carbohydrates can be made up of disaccharides, which is simply two single monomers of sugar linked together. Lastly, polysaccharides contain multiple chains of sugar monomers that are linked with each other (Karp Gerald). Lipids consist of a collection of molecules that happen to be insoluble in water, however they are very soluble in non-polar solvents. Typically, lipids include oils and fats, phospholipids, and steroids (Albert, B 1980). Nucleic acids are molecules that are within the cell that collect and process any genetic or hereditary information and are polymers of nucleotides (Karp Gerald 2013). Lastly, proteins are polymers that are made up of amino acids. Proteins have a many purposes, one being the responsibility of the shape and structure of the cell (Karp Gerald 2013).

        The experiment performed was designed to identify which macromolecules are present in the twelve substances acquired from a series of basic tests. The three basic tests included; iodine test to determine which solution contains starch and glycogen, Benedict’s test to determine which solution contains reducing sugars and lastly biuret test to determine which solutions contain proteins. In order to identify each macromolecule properly, a change in colour will occur in the three different tests. The purpose of the iodine test is to test for the presence of starch or glycogen within the sample. Once iodine is added to the solution, the solution colour will change to a blue-black in the presence of starch, and turn reddish-brown when glycogen is present within the sample (“Starch-idoine test”, 2008). The Benedict’s test is used to determine the presence of reducing sugars. In order to determine this, the solutions will experience a colour change to a yellow-green or a red-brown range, which will ultimately indicate whether or not a reducing sugar is present. Finally, the biuret test indicates if proteins are present within the substance. In order to determine the presence of protein in the solution, Copper (II) sulfate is added, which will cause the Copper (2+) to react with peptide bonds, resulting in a violet colour solution (Pollard, T. D., & Earnshaw, W. C. 2004).

Materials and Methods:

        Please refer to pages 16 to 20 of the Fall 2015 Biology 130L Lab Manual for the materials and methods of the lab. All steps were followed with no deviation.

Results:

Test 1: Iodine Test

• Table 1: Iodine test results when iodine is mixed with the twelve solution samples. Positive results will yield a blue-black colour change

Test 2: Benedict’s Test

• Table 2: Benedict’s test results when Benedict solution is mixed with the twelve solutions. Positive results yield a red/brown colour change.

Test 3: Biuret Test

• Table 3: Biuret test results when sodium hydroxide and copper sulfate is mixed with the twelve solutions. Positive results will yield a violet colour change.

Discussion:

        The sole purpose of the iodine test was to properly identify which of the following twelve sample solutions contained starch or glycogen. Starch is a polysaccharides which is produced by plants during the process of photosynthesis. As previously stated, starch contains multiple sugar monomer and is joined in a 1, 4 linkage (Karp Gerald 2013). Starch may be separated into amylose and amylopectin, in which case 10-20% is consumed by amylose and 80-90% is consumed by amylopectin (Ophardt, 2003). Ultimately, carbohydrates are also polysaccharides and the main source of storage location of this source is within higher organisms such as animals and humans (Ophardt, 2003).

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