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 CO2 and H2O 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 carbohydrate in nature – particularly cellulose, hemicelluloses and lignin. Carbohydrates comprise a comprehensive group of naturally occurring substances, which include innumerable sugars and sugar derivatives, as well as high-molecular weight carbohydrates (polysaccharides) like starch and cellulose in plants and glycogen in animals. A polysaccharide molecule is composed of a large number of sugar or sugar-like units. Carbohydrates are of great importance in biology. The unique reaction, which makes life possible on Earth, namely the assimilation of the green plants, produces sugar, from which originate, not only all carbohydrates but, indirectly, also all other components of living organisms. Carbohydrates form a very large group of naturally occurring organic compounds which play a vital role in daily life. They are produced in plants by the process of photosynthesis. The most common carbohydrates are glucose, fructose, sucrose, starch, cellulose etc. Chemically, the carbohydrates may be defined as polyhydroxy aldehydes or ketones or substances which give such molecules on hydrolysis. Many carbohydrates are sweet in taste and all sweet carbohydrates are called as sugars. The chemical name of the most commonly used sugar in our home is sucrose.
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