Topic: SciencesChemistry

Last updated: September 16, 2019

QualificationHigher National Diploma in Biomedical ScienceLevel5Module Name NumberBiochemistry (BIOM 502/1)Name of CandidateFathmath DheemaStudent Number516031822Title of PracticalChemical Tests for BiomoleculesDate of Practical25th April 2018Submission Date9th May 2018 MARKS SCHEME LABORATORY REPORTIntroduction and Objectives/ 20Materials and Methodology/ 20Results/ 20Discussion and Conclusion/ 20Academic Writing/ 10Log Book / 10TOTAL / 100 Contents Introduction Biomolecules are those primarily made up of carbon, hydrogen, and oxygen and are synthesized by living organisms. The most common group of biomolecules known as macromolecules, which are large in size, include carbohydrate, protein and lipids. Each of these macromolecules are made up of small monomers. ( Donohue, 2018).

Carbohydrates, also known as saccharides or sugars, are the most abundant molecule found in nature. They are made up of monomers called monosaccharides. Examples of monosaccharides include, dextrose, levulose etc. (Introduction to Biomolecules, 2012). Monosaccharides are used to build cell structuresa and they also function as an energy source during cellular rrespiration. When two monosaccharides join together they form a dissaccharide. For exmaple Galactose ( figure1.) is formed from lactose combined with glucose.

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And polysaccharides are formed when a long chain of monosaccharides bond together, like starch which is composed of many alpha glucose molecules joined together. They act a source of energy in human body in the form of glycogen and in plants, in the form of starch. And also they componenets of other molecules such as DNA, and RNA. Lipids are biomolecules that consists of glycerol and fatty acid tails. These fatty acid tail are composed of long chain of carbon and hydrogens and are hydrophobic, which can either be saturated or non saturated. They play an important role in energy storing, as they store more amount of energy than carbohydrates.

Lipid together with a phosphate group forms a phospholipid which is an important componenet of the cell memebrane. All organelles from mitochondria to nuclues, are surrounded by lipids. Many amino acids join together to form the complex structure of a protein. The 20 amino acid that forms a protein, are similar in structure except for the R group in each amino acid, as in figure 2a which shows Alanine with the R group CH3 and figure 2b. shows Cysteine with CH2 SH. (VirtualChembook,2003) Proteins play many vital roles in our body, from providing support to be regulatory proteins such as enzymes which helps in cell processes.

Our immune system contains antibodies which are made up of proteins. (staff, 2013). This lab report is about the chemical tests that was done to identify the biomolecules in unknown samples of carbohydrates, amino acids, and lipids. The specific functional groups of biomolecules are distinguished with the help of these of these tests. First of all, for identification of carbohydrates, there are 6 tests iodine test used to test for the presence of starch. When starch react with iodine solution a bluish color is obtained. (Arshad, 2015) 2.

Molischs test When concentrated sulphuric acid is treated with a carbohydrate, it is dehydrated to form furfural derivatives, when Alpha naphthol is added they condense to form a colored compound. 3. Benedict test this test is mainly used to identify reducing sugars and it can also detect carbohydrates with free aldehyde and ketone groups, which has the ability to reduce certain metallic ions.

(Chabra, 2014) 4. Tollens test used to distinguish between aldehyde and ketones. Tollens solution readily oxidizes aldehydes but doesnt oxidize ketone.

(Nichols, 2017) 5. Barfoed test this test is to tell apart monosaccharaides and disaccharides. Monosaccharaides reacts faster than disaccharides. 6. Seliwanoffs Reaction (for ketose sugars) when HCL keto hexoses is treated with HCL form 5-hydroxy methyl furfural, and then condenses to give a red colored complex. (Chabra, 2014). Secondly, the tests for amino acids include 1.

Ninhydrin test this test is common for all amino acids. Ninhydrin reacts with the amino group to form a blue substance. But since proline has an imino group, it forms a yellow substance and arginine reacts with Ninhydrin to form a brown colored product.

2. Xanthroproteic test aromatic R groups containing amino acids, such as tyrosin, tryptophan and phenylalanine can be detected through this test. The aromatic benzene ring undergoes nitration to from a yellow colored compound. Since phenylalanine is difficult to titrate under normal condition it gives a negative or slightly positive result.

4. Millions test this test is specific to detect the presence of tyrosine and protein containing this amino acid as it is the only amino acid that contains a hydrobenzene ring in it. When tyrosin and millions reagent is reacted together it gives a yellow precipitate, upon heating it changes into red colored precipitate. (Karki, 2018) 5.

Paulys test Objectives To identify unknown samples of carbohydrates To discriminate reducing sugar from non-reducing sugars To identify certain amino acids To identify which is more translucent among water and oil To identify ketoses Materials Test tube rack Test tube holder Bunsen burner Test tubes Beaker For carbohydrate tests 3 unknown carbohydrate samples ( A, B, C) Molischs reagent Concentrated H2SO4 Iodine solution Benedicts solution AgNO3 Dilute Sodium hydroxide Dilute NH4OH Bafoed reagent Seliwanoffs reagent For Amino acid tests Ninhydrin solution Concentrated HNO3 Millions reagent Sulphanilic acid 25 NaNO2 Dilute HCL 2 NaOH For lipid tests Cooking oil Ethanol Distilled water Unglazed brown paper Cotton swab Water Sudan 3 red solution PAGE MERGEFORMAT 15 Figure SEQ Figure ARABIC 1. Structure of an Alpha Galactose. (Chemistry, 2004) Figure SEQ Figure ARABIC 2b. cysteine Figure SEQ Figure ARABIC 3a. Alanine fimEv -ui/gSC_O h Q_qQ j7-az,fp_x/v Av ygi_ oZo.

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