Glucose condensation reactions

C13-0108. The first step of glucose metabolism is an enzyme-catalyzed condensation reaction between phosphoric acid and the CH2 OH hydroxyl on glucose. Draw the structure of this glucose phosphate. 

C14-0082. Glucose and fructose combine to make sucrose in a condensation reaction for which... 

The addition of glyceraldehyde dimer had a significant impact on the catalysis of glucose. CrCf is the preferred catalyst and resulted in a 94% conversion of glucose with a 70% yield of HMF. In the presence of glyceraldehyde the conversion decreased to about 60% and the yield of HMF fell to 20%. This means that HMF selectivity also decreased (selectivity = yield/conversion). The loss of selectivity was primarily due to formation of heavies via intermolecular condensation reactions. The heavies were not characterized. 

Glucose is the simplest carbohydrate. It is found in grapes and corn syrup. Fructose gives fruit its sweet taste. A condensation reaction between glucose and fructose produces sucrose, commonly called table sugar. Sucrose is found in sugar cane and sugar beets. 

The rapid spontaneous mutarotation of glucose-6-phosphate has been shown to result from an intramolecular catalysis of the reaction by the phosphate group at carbon 6 (81). The cleavage of glucose into three carbon fragments, which is essentially a reversal of the aldol condensation reaction, requires the ketohexose as substrate. The necessary isomerization reaction to form the ketohexose then uses the open-chain form intermediate of the mutarotation reaction. Salas et al. (80) have speculated that the enhanced mutarotation of glucose-6-phosphate may thus have been the key requirement which led to the evolution of the phosphorolytic pathway for glucose metabolism. 

Melanoidin polymers compounds produced from condensation reactions of glucose with acidic, neutral, and basic amino acids. 

Approximately twice as much l-C14-D-mannose as l-C14-D-glucose is obtainable from D-arabinose by the nitromethane synthesis when no excess of CM-nitromethane is employed in the initial condensation reaction. 

A condensation polymer is one in which the repeating unit lacks certain atoms which were present in the monomer(s) from which the polymer was formed or to which it can be degraded by chemical means. Condensation polymers are formed from bi- or polyfunctional monomers by reactions which involve elimination of some smaller molecule. Polyesters (e.g., 1-5) and polyamides like 1-6 are examples of such thermoplastic polymers. Phenol-formaldehyde resins (Fig. 5-1) are thermosetting condensation polymers. All these polymers are directly synthesized by condensation reactions. Other condensation polymers like cellulose (1-11) or starches can be hydrolyzed to glucose units. Their chemical structure indicates that their repealing units consist of linked glucose entities which lack the elements of water. They are also considered to be condensation polymers although they have not been synthesized yet in the laboratory. 

The reaction is the reverse of the condensation reaction by which sucrose formed. In humans, polysaccharides, such as starch and glycogen, and disaccharides, such as sucrose, are broken down in this way to make glucose. 

When glucose and fructose bond together, the disaccharide sucrose is formed. Note that water also is a product of this condensation reaction. Remember that each ring structure is made of carbon atoms, which are not shown for simplicity. 

The energy stored in the a(l 4) glycosidic bond during the condensation reaction in glycogen synthesis is sufficient to permit the formation of a glucose-phosphate bond without using ATP. 

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