Background - Background Information on Carbohydrates,...

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What are polymers? All living things are composed of organic (carbon-based) molecules. The four major groups of organic molecules are carbohydrates, lipids, proteins, and nucleic acids. Each of these molecules, although structurally and functionally different, has a common tie in their manufacture: each molecule is comprised of smaller sub-units called monomers , which have been combined via condensation or dehydration reaction, or loss of water. All of the biologically important molecules discussed in this portion of the lab are created by the removal of one molecule of water between monomers. Figure 1: Formation of a polymer through a condensation reaction (a.k.a. dehydration synthesis). Carbohydrates What are monosaccharides (1 sugar), disaccharides (2 sugars), polysaccharides (many sugars)? Carbohydrates are classified by the number of individual sugar molecules that they contain. They have roughly equal numbers of carbon and oxygen atoms (n) , and twice that number (2n) of hydrogen atoms . An approximate chemical formula for a typical carbohydrate is (CH 2 O) n where “n” is an integer (3, 4, 5, etc.). The most common monosaccharides or simple sugars are the six carbon sugars known as glucose, fructose and galactose , the most important one being glucose. They all have the same molecular formula, C 6 H 12 0 6 but slightly different structural formulas and slightly different chemical properties. Monosaccharides bonded through dehydration synthesis form disaccharides through one glycosidic bond. Disaccharides such as sucrose, maltose , and lactose contain two sugar monomers. Disaccharides such as maltose (glucose + glucose), sucrose or table sugar (glucose + fructose) , and lactose or milk sugar (glucose + galactose) have the same molecular formula, C 12 H 22 0 11 but slightly different structural formulas and slightly different chemical properties. Polysaccharides, such as starch, glycogen, cellulose, and chitin , contain many sugar monomers linked together. Starch is a polysaccharide produced by plants. Glycogen is a polysaccharide produced by animals. These molecules are large and are usually insoluble in water. What are Reducing Sugars? Reducing sugars are carbohydrates that, when combined with a specific chemical reagent called Benedict’s reagent, are participants in an oxidation-reduction (redox) reaction with the Benedict’s. When combined with the chemical reagent Benedict’s, the reducing sugar is oxidized The Benedict’s reagent is reduced during the reaction. The Benedict's reagent contains blue copper(II) sulfate (CuSO 4 ) which is reduced to red copper(I) oxide (Cu 2 O) by the reducing sugar. 1
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This note was uploaded on 04/07/2008 for the course BIOSCI 0050 taught by Professor Carollafarve during the Fall '07 term at Pittsburgh.

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Background - Background Information on Carbohydrates,...

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