IDENTIFYING DIFFERENT BIOLOGICAL MACROMOLECULES
Introduction
Biological macromolecules consist of very small organic molecules that are linked together to produce large molecules (Garcia, 2002). These large molecules are called polymers (Garcia, 2002). In particular, for macromolecules like carbohydrates and proteins, the polymer molecule is created when small molecules called monomers are covalently bonded to one another (Garcia, 2002). There are four major types of biological macromolecules. The four groups are carbohydrates which consist of polysaccharides and monosaccharides, proteins, lipids and nucleic acids (Garcia, 2002). Biological macromolecules are relevant because they are the building blocks of cells in both animals and plants (Karp, 2010). These types of molecules not only form the structure of a cell, but also carry out the cells' activities (Karp, 2010). The existence of macromolecules in living organisms is what provides life and separates them from the rest of the world (Karp, 2010). The purpose of this experiment is to test for the presence of macromolecules in various liquid solutions. In this lab we will explore two of the four types: carbohydrates and proteins. In carbohydrates the monomer unit is called a simple sugar while in proteins the monomers that are linked together are called amino acids (Garcia, 2002). Particularly, in carbohydrates when a simple sugar is present it is referred to as a monosaccharide and when a bunch of monosaccharides are attached to one another covalently a complex sugar is formed known as a polysaccharide (Garcia, 2002). Carbohydrates are simply molecules that are made up of sugars (Garcia, 2002). Their molecules contain simple elements like carbon, hydrogen and oxygen and an example of a carbohydrate would be glucose (Garcia, 2002). Within living organisms like ourselves, proteins are considered to be very diverse and complex molecules (Garcia, 2002). Some things that are composed of proteins include muscle tissue, blood cells and enzymes (Garcia, 2002). Like carbohydrate molecules, protein molecules also contain simple elements like carbon, hydrogen and oxygen but these molecules also contain nitrogen as well (Garcia, 2002). A simple example of protein would be any type of meat. Within this experiment we will be testing for 3 types of carbohydrates which are starch, glycogen and reducing sugars. Starch is a polysaccharide molecule that is commonly found in plants as a source of storage (Karp, 2010). It is composed of amylose and amylopectin which are considered two types of glucose polymers (Karp, 2010). Glycogen is also a polysaccharide molecule, however, it is commonly found in animals as a source of storage (Karp, 2010). Glycogen is considered a glucose polymer that contains many branches of molecules (Karp, 2010). Reducing sugars are simply monosaccharides that are linked together by single bonds of carbon atoms. An example of a reducing sugar is glucose (Karp, 2010). Within this experiment 3 types of tests will be used and they are the Iodine test for starch and glycogen, Benedict's test for reducing sugars and the Biuret test for protein. The iodine test is a test used to test for the presence of starch molecules which are polysaccharides (Garcia, 2002). Initially, a sample amount of iodine is added to a specific solution (Garcia, 2002). If the colour of the solution turns blue-black then the test is positive and there is a presence of starch molecules within the solution (Garcia, 2002). If the colour of the solution is reddish-brown the test is also positive, however, there is now a presence of glycogen molecules in the solution (Garcia, 2002). If the colour of the solution turns yellow then the test is negative and there is no presence of starch or glycogen (Garcia, 2002). The Benedict's test is used to test for the presence of a monosaccharide called glucose in the solutions (Garcia, 2002). To test for the presence of glucose a clear blue liquid known as Benedict's reagent is used which contains copper (+2) ions (Garcia, 2002). When this reagent is mixed and boiled with any solution containing trace amounts of glucose the copper (+2) ions reduce to copper (+1) ions and then become oxidized to form copper oxide (Garcia, 2002). In Benedict's test a positive test is when the colour of the solution changes to a red-brown or orange-brown when the reagent is added (Garcia, 2002). The Biuret test is used to test for the presence of protein molecules in solution (Garcia, 2002). To test for the presence of protein, a liquid known as Biuret reagent which also contains copper ions is added to a solution (Garcia, 2002). When the reagent is added to solution the coppers ions react with the linked protein groups to produce a violet colour (Garcia, 2002). In the Biuret test the only colour that signals a positive test result is the colour violet (Garcia, 2002).
