Macromolecules Lab Report

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Introduction Macromolecules are the most abundant organic molecules living in a cell. The elements in a living material are carbon, oxygen, nitrogen, hydrogen, nitrogen, sulphur, and phosphorus. All these elements combine in a discrete way to form the molecules of a biological system. The four major biological macromolecules are carbohydrates, lipids, proteins and nucleic acids (Miskovic Dragana , Department Of Biology). In this lab, the purpose of this experiment is test for evidence of starch, glycogen, reducing sugars and protein through a series of tests. These tests include the iodine test for starch and glycogen, Benedict’s test for reducing sugars and biuret test for protein. The iodine test is used to determine if glycogen…show more content…
This experiment includes filling the tubes with the eleven known substances and the one unknown substance (#202) and adding Benedict’s solution to each tube. Then, place the tubes in boiling water and detect the colour change. There are two types of forms of sugars; the straight chain form and the ring form. The straight chain form has an aldehyde group which reacts in the Benedict’s solution and which also makes glucose a reducing sugar. The ring form does not react because there is no aldehyde group present in the chain (Reush,2013) . The benedict’s solution contains Cu²+ ( cupric ions) and this can be reduced to Cu+ (cuprous ions) due to reducing sugar (Miskovic Dragana , Department Of Biology) . To detect the presence of reducing sugar in the test, the colour of the Benedict solution and the substances will change to a yellow, green, red or a brown mixture. The biuret test is used to determine the presence of protein in the twelve substances. This experiment includes filling the tubes with the eleven known substances and the one unknown substance (#202) and adding the 10% of NaOH (sodium hydroxide) to each tube. Mix it thoroughly to detect the colour change. Protein is made up of amino acids linked by peptide bonds, using alkaline solution we will be able to determine the existence of peptide bonds and protein. To detect the presence of protein in the substances,…show more content…
The three solutions came out positive and out of the three solutions; only one came out positive for glycogen which was 1% glycogen solution and the other two are 1% starch solution and the unknown solution (#202). Glycogen showed obvious results with the quick change in colour from original to reddish-brown. Thus, showing glycogen was present. The result of starch is also predictable to test positive, the change is obvious when it changes from colourless to blue-black which indicates starch existed. Glycogen and starch are categorized as complex carbohydrates and when iodine solution comes in contact, it went through a chemical reaction to form a brown and a blue colour substance (Berg, 2002). Glycogen turns reddish-brown due to the multibranched components (Berg,2002). Amylopectin which is a soluble polysaccharide, is branched and only binds a small amount of iodine to produce the reddish-brown. Starch is a mixture of amylose (linear) and amylopectin (branched). The colour changed for starch and iodine reacted due to the mixture of amylose and iodine. Amylose consists of single, unbranched chains of glucose molecules (Garfield, 2008). During the mixture of iodine and the 1% starch solution which is present in starch, the iodine gets stuck in the braid of the beta amylose-molecules (Berg,2002). The starch than forces the iodine into a linear arrangement in

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