Ten-carbon sugars

As the name implies, carbohydrates are characterized by a nominal (CH20) composition. Next to proteins, carbohydrates combined into polysaccharides are generally the most abundant (Table 8.6) and widely distributed biopol5miers in living organisms. (However, there are some plankton in which the lipid concentration exceeds that of carbohydrates (Wakeham et al, 1997).) The fundamental monomeric rmits of most carbohydrates are five- (pentose) and six-(hexose) carbon sugars, of which there are roughly ten common forms (Fig. 8.9). These structural units usually occur as either aldoses or ketoses, in which either the first (aldose) or second (ketose) carbon... 

The shikimic acid pathway requires the C4 sugar erythrose-4-phosphate, and phosphoenol pyruvic acid (a derivative of pyruvic acid, locked in its enol form, see Figures 1.1 and 2.19) as starting materials. The route to aromatic compounds has more steps than those met earlier, and, not surprisingly, for a plant process, uses sugar derivatives as starting materials. A total of ten carbon atoms are required, four from erythrose, and six from two molecules of pyruvate one of these is later lost as CO2. The final product therefore is a C9 compound, so that such products are... 

C ( amorphous/ charcoal). Thiele1 studied the heat of combustion of charcoal prepared from sugar as a function of the temperature of preparation, and found that the heat of combustion was constant only for samples prepared above 1400°. The data of Thiele,1 Mixter,3 and Favre and Silbermann,1-5-11 yield, respectively, 96.4, 96.6, and 96.4 for the heat of the reaction, C ( amorphous, charcoal) +02 (g) =CC>2 (g). Data on the heat of combustion of this form of carbon were also reported by-Peterson,111 Despretz,1 Berthelot and Petit,2 Dulong,2 Andrews,14 16 Berthelot and Vielle,7 12 Ruff and Gersten,2 Thomsen,7 16 Pfaundler,3 Niki-ten,1 and Lavoisier and Laplace1 (see Mellor1). 

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