Hydroxyl group carbohydrate component

The nucleotides of RNA and DNA consist of three components a carbohydrate, a phosphate group and an organic nitrogenous base. There are two types of carbohydrate molecule in nucleic acids, both of which are D-pentoses, i.e. contain five carbon atoms. The carbohydrate in RNA is ribose, while DNA contains deoxyribose, which has a hydrogen atom instead of a hydroxyl group attached to the carbon in the 2 position (Figure 13.1). 

The component typically analyzed in plants is cellulose, which is the major structural carbohydrate in plants (Epstein et al. 1976, 1977). Cellulose contains 70% carbon-bound hydrogen, which is isotopically non-exchangeable and 30% of exchangeable hydrogen in the form of hydroxyl groups (Epstein et al. 1976 Yapp and Epstein 1982). The hydroxyl-hydrogen readily exchanges with the enviromnen-tal water and its D/H ratio is not a useful indicator of the D/H ratio of the water used by the plants. 

Carbohydrates are the most abundant organic component of plants. Structurally, carbohydrates are usually polyhydroxy aldehydes or polyhydroxy ketones (or compounds that hydrolyze to yield polyhydroxy aldehydes and ketones). Since carbohydrates contain carbonyl groups and hydroxyl groups, they exist primarily as acetals or hemiacetals. 

In the crystalline complex, solvent molecules can be bonded not only to the cation, but also to the anion and the carbohydrate. A detailed x-ray study has snown that, in sucrose NaBr 2 HjO, each Br ion has bonds to one water molecule, one Na ion, and four carbohydrate hydroxyl groups.00 The ability of a complex to possess solvent of crystallization, even when the free individual components themselves are incapable of doing so under the same conditions of temperature, is exemplified by the formation of sucrose Nad 2 H2O at room temperature. Sucrose and sodium chloride crystallize from their aqueous solutions in the nonhydrated form. 

TiTany commercial uses of carbohydrates depend upon reversible inter- actions of the hydroxyl groups with ions to form complexes. The processes are intricate, and analyses of the equilibria involved have been difficult or impossible (I). For example, the nature of the complexes involving polysaccharides and polyanions, such as borate, can only be hypothesized (2). Similarly the gelling of pectates with Ca(II) (3), the reactions of heptono-y-lactones with Fe(III), or the nature of Fe(III)-dextran complexes in intramuscular injectable solutions are awaiting proper description. Although the systems involving monomeric components are more amenable to study, as for the reactions of metal salts or hydroxides with monosaccharides or their simple derivatives (4,5, 6, 7)... 

Gangliosides were labelled with galactose. In the fetal cell lines (FHS) and SKCO-1 there was no marked difference between treated and untreated cells. In HT-29, SW-480, and Sw-620 cell lines, the amounts of Gm3 appeared to remain the same, but the distribution of Gm3 components was affected by butyrate. These changes, might be due to alterations in the lipid moieties or, alternatively, there might be an acetylation Of a hydroxyl group in the carbohydrate moiety, since it has been shown that the butyrate increases the amount of acetylated histones. 

Some chemical reactions of the wood components involve functional groups that do not form part of the polymer chain and may have only a slight effect on some wood properties and may enhance some. For example, esterification or etherification of free hydroxyl groups in carbohydrates or lignin may reduce hygroscopicity, increase dimensional stability, and actually increase wood strength by reducing the equilibrium moisture content. 

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