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Biomolecules

  Biomolecules   A living system grows, sustains and reproduces itself. The most amazing thing about a living system is that it is composed of non-living atoms and molecules. The pursuit of knowledge of what goes on chemically within a living system falls in the domain of Biochemistry. Even though there are thousands of different types of molecules in a cell, there are only a few basic classes of bimolecular like carbohydrates, proteins, nucleic acids, lipids, etc. Proteins and carbohydrates are essential constituents of our food. In addition, some simple molecules like vitamins and mineral salts also play an important role in the functions of organisms. The complexity of even the simplest of life forms, the single cell, cannot be overstated. Nevertheless, from a chemical perspective, cellular components can be segregated into macromolecules (DNA, RNA, proteins, etc.), relatively simple molecules (amino acids, monosaccharide’s, and lipids), and their precursors: CO 2 ,H 2 O, and NH 3 .
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Carbohydrates

  Carbohydrates Carbohydrates are the most abundant bimolecule belonging to class of organic compounds found in living organisms on earth. Each year, more than 100 billion metric tons of CO 2  and H 2 O are converted into cellulose and other plant products due to photosynthesis. Living matter is largely made of bimolecule consisting of water and complex polymers of amino acids, lipids, nucleotides and carbohydrates. Carbohydrates are most special of them in that they remain associated with the three other polymers mentioned. Carbohydrates are linked with amino acid polymers (proteins) forming glycoprotein’s and with lipids as glycolipids. Carbohydrates are present in DNA and RNA, which are essentially polymers of D-ribose-phosphate and 2-deoxy-D-ribose phosphate to which purines and pyrimidines bases are attached at the C-1 reducing position. Carbohydrates are a widely diverse group of compounds that are ubiquitous in nature. More than 75% of the dry weight of the plant world is carboh
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Classification of Carbohydrates

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  Classification of Carbohydrates Carbohydrates are classified into three groups depending upon their behavior on hydrolysis.   i. Monosaccharide’s: A polyhydroxy aldehyde or ketone which cannot be hydrolyzed further to a smaller molecule containing these functional groups is known as a monosaccharide. About 20 monosaccharides occur in nature and glucose is the most common amongst them. Monosaccharides are further classified on the basis of the number of carbon atoms and the functional group present in them. If a monosaccharide contains an aldehyde group, it is known as an aldose and if it contains a keto group,it is known as a ketose. The number of carbon atoms present is also included while classifying the compound as is evident from the examples given in Table 1. Glucose occurs freely in nature as well as in the combined form. It is present in sweet fruits and honey. Ripe grapes also contain glucose in large amounts.   ii.  Disaccharides: Carbohydrates which give two monosaccharide
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Structure of Monosaccharide’s

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  Structure of Monosaccharide’s Although a large number of monosaccharide’s are found in nature, we will confine our discussion here to four of them only viz. D-glucose, D-fructose, D-ribose and 2-deoxy-D-ribose. D-Glucose (an aldohexose) is the monomer for many other carbohydrates. Alone or in combination, glucose is probably the most abundant organic compound on the earth. D-Fructose (a ketohexose) is a sugar that is found withglucose in honey and fruit juices. D-Ribose (an aldopentose) is found in ribonucleic acids (RNA) while. 2-Deoxy-D-ribose is an important  constituent of the deoxyribonucleic acids (DNA). Here, the prefix 2-Deoxy indicates that it lacks oxygen at carbon no. 2 These monosaccharides generally exist as cyclic compounds in nature. A ring is formed by a reaction between the carbonyl group and one of the hydroxyl groups present in the molecule. Glucose preferentially forms the six member rings which can be in two different isomeric forms called α- and ß-forms (shown b
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Structure of Di Saccharides and Polysaccharides

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  Structure of Di-Saccharides and Polysaccharides Disaccharides are formed by the condensation of two monosaccharide molecules. These monosaccharides join together by the loss of a water molecule between one hydroxyl groups on each monosaccharide. Such a linkage, which joins the monosaccharide units together, is called glycoside linkage. If two α-glucose molecules are joined together, the disaccharide maltose is formed Similarly, sucrose (the common sugar) consists of one molecule of glucose and one molecule of fructose joined together. Lactose (or milk sugar) is found in milk and contains one molecule of glucose and one molecule of galactose. If a large number of monosaccharide units are joined together, we get polysaccharides. These are the most common carbohydrates found in nature. They have mainly one of the following two functions- either as food materials or as structural materials. Starch is the main food storage polysaccharide of plants. It is a polymer of α-glucose and consist
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Importance of carbohydrates

  Importance of carbohydrates Carbohydrates are of great importance in biology. The unique reaction, which makes life possible on the Earth, namely the assimilation of the green plants, produces sugar, from which originate, not only all carbohydrates but, directly or indirectly, all other components of living organisms. The carbohydrates are a major source of metabolic energy, both for plants and for animals that depend on plants for food. Aside from the sugars and starch that meet this vital nutritional role, carbohydrates also serve as a structural material (cellulose), a component of the energy transport compound ATP, recognition sites on cell surfaces, and one of three essential components of DNA and RNA. Importance can be considered under following headings;   Metabolic/Nutritional   The important role of carbohydrates, generally, in the metabolism of living organisms, is well known. The biological breakdown of carbohydrates (often spoken of as "combustion") supplies the
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Rare sugars

  Rare sugars            Rare sugars are defined by the International Society of Rare Sugars (ISRS) as monosaccharide’s and their derivatives that are rare in nature. They are hardly available for research purposes because of their expensiveness. "Izumoring", a structural framework containing all 34 six-carbon monosaccharide’s linked by enzymatic reactions, has been proposed following the discovery of a key enzyme that converts abundantly occurring monosaccharide’s in nature into rare sugars. This has made possible the mass production of rare sugars from inexpensive sugars such as D-glucose or D-fructose. Rare Sugars are mostly used in pharmaceuticals as precursors for a wide variety of carbohydrate-based drugs. These include nucleoside analogues, which are used in antiviral applications such as HIV, HBV and HCV. Another important class of compounds is complex oligosaccharides and olignonucleotides, which may be used as anti-inflammatory or anti-cancer agents, as well as in h
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