Experimenting with Biological Macromolecules in Various Identification Tests

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Macromolecules are highly important organized organic molecules that are found within living cells. These biological molecules help the body execute precise important tasks. There are four types of macromolecules: carbohydrates, lipids, proteins and nucleic acids. (Karp, 2010) This specific experiment showcased the identification of different macromolecules using three different testing methods. Carbohydrates, sugar molecules, are known as “fast fuel” in the body, and they contain base elements of carbon, oxygen and hydrogen. (Lea, 2002) The simplest carbohydrate molecule is known as a monosaccharide, which is a simple sugar. Monosaccharide’s can be joined together by a covalent glycosidic bond to create more complex sugars such as disaccharides (2 monosaccharide’s), oligosaccharides (between three to ten monosaccharide’s) and polysaccharides (consists of several monosaccharide’s). (Karp, 2010) Starch is the most common nutritional polysaccharide, which consists of two polymers: amylose and amylopectin. Amylose is unbranched whereas amylopectin is branched. Structural polysaccharides consist of cellulose, which is a major component of plant cell walls; chitin, which is a tough outer covering of invertebrates; and glycosaminoglycans (GAGs). (Karp, 2010)

Lipids help produce energy within the body. Lipids are hydrophobic (“water-hating”), which makes it harder to break down into energy for the body. Steroids, fats and phospholipids are different functional forms of lipids. Steroid molecules are created around a four-ringed hydrocarbon skeleton and provide aid in the synthesis of many steroid hormones. (Karp, 2010) Triglycerides are composed of three fatty acid molecules and one glycerol molecule that is bonded with an ester linkage. Fats that are liquid at room temperature are classified as being an oil. (Karp, 2010) Triglycerides and phospholipids both share a glycerol molecule. Their major difference is that the phospholipids only contain two fatty acids, instead of three, and they also contain a phosphate group that is covalently bonded to a polar head group. (Karp, 2010)

Proteins are the macromolecules that carry out the most functions. Some of proteins complex functions include: acting as enzymes, hormones, antibodies, toxins, light absorption and refraction, transporting substances from one area of the body to another and a few more important functions. (Karp, 2010) Amino acids are the monomers of proteins and are bonded together in unique combinations to create polypeptide chains and finally the chain is folded into a “unique functional protein”. (Lea, 2002) The whole process of protein formation occurs during DNA transcription and translation by RNA. (Lea, 2002)

Nucleic acids are composed of long strands of monomers called nucleotides. Nucleotides consist of three important parts: a five-carbon sugar (pentose sugar), a phosphate group and a nitrogenous base. There are two types of nucleic acids found amongst living organisms, double-stranded deoxyribonucleic acid (DNA) and single-stranded ribonucleic acid (RNA). Deoxyribonucleic acids provide all the genetic information of all cells whereas ribonucleic acid reads the information and helps carry out the messages of DNA. (Karp, 2010)

For each of the three testing methods, the Iodine Test, Benedict’s Test and the Biuret Test, distilled water acted as the negative control and helped prove which sample solutions were indeed positive or negative. The Iodine Test for starch and glycogen was the first testing method used in this experiment. Iodine solution has a base colour of pale yellow without contact with other solutions. Distilled water, being the negative control, showcased that the resulting colour of the solution would have to resemble a dark yellow liquid. A positive result for the iodine test was presented with the resulting colour change of the sample solution being violet-blue-black. (Gurien, 2008) Secondly, Benedict’s Test for...
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