Carbohydrates, structural

Cellulose and starch are macromolecules with empirical formulas that resemble hydrated carbon, CX (H2 0)y, where x and y are integers. The monomers from which these macromolecules are consfructed are sugars such as glucose and fructose. These monomers and macromolecules are the carbohydrates. Structurally, carbohydrates are very different from simple combinations of carbon and water. Even the smallest carbohydrates contain carbon chains with hydrogen atoms, OH groups, and occasional ether linkages. 

Dietary fibre, which comprises all the non-digestible structural carbohydrates of plant cell walls and any associate lignin, provides a further example of a complex food-borne factor which cannot be classified as a nutrient, and which continues to generate debate over such issues as definition and analytical techniques. However, whatever the unresolved complexities, dietary fibre has a lengthy history and had proved itself eminently suitable as a component of functional food products long before the term was even coined. 

The lower rates of nutrient absorption associated with diets high in nonstarch polysaccharides are probably due to the increased viscosity of digesta (Vaugelade et al., 2000), which increases the thickness of the unstirred layer overlying the enterocytes and causes anon-specific decline in solute absorption. This explains why diets high in 3-glucans, which are structural carbohydrates and which increase viscosity of digesta, reduce absorption of nutrients and... 

Wunschel, D. K. Fox, K. Black, G. Fox, A. Discrimination among the Bacillus cereus group, in comparison to B. subtilis, by structural carbohydrate profiles and ribosomal RNA spacer region PCR System. Appl. Microbiol. 1994,17, 625-635. 

Carbohydrate metabolism in the organism tissues encompasses enzymic processes leading either to the breakdown of carbohydrates (catabolic pathways), or to the synthesis thereof (anabolic pathways). Carbohydrate breakdown leads to energy release or intermediary products that are necessary for other biochemical processes. The carbohydrate synthesis serves for replenishment of polysaccharide reserve or for renewal of structural carbohydrates. The effectiveness of various routes of carbohydrate metabolism in tissues and organs is defined by the availability of appropriate enzymes in them. 

The hydrothermal carbons obtained in the end from soluble, non-structural carbohydrates are micrometer sized, spherically shaped particle dispersions, containing a sp2 hybridized backbone (also responsible for the brown to black color) decorated with a dense layer of polar oxygenated functionalities still remaining from the original carbohydrate. The presence of these surface groups offers the possibility of further functionalization and makes the materials more hydrophilic and well-dispersible in water. The size of the final particles depends mainly on the carbonization time and precursor concentration inside the autoclave, as well as additives and stabilizers potentially added to the primary reaction recipe. An SEM image of a model reaction illustrating this dispersion state is shown in Fig. 7.1. 

Manners, D. J. (1989). Recent developments in our understanding of amylopectin structure. Carbohydr. Polym. 11, 87-112. 

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. 

L. Hough, A. C. Richardson, and L. A. W. Thelwall, Reaction of lactose with 2,2-dimethoxypropane. A tetra-acetal of novel structure, Carbohydr. Res., 75 (1979) C11-C12. 

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. 

Mischnick, R, Kuhn, G. (1996). Model studies on methyl amyloses correlation between reaction conditions and primary structure. Carbohydr. Res., 290, 199-207. 

Kaushalya, G., . K. Thakral, S. K. Arora, M. L. Chowdhary, and K. Gupta. 1996. Structural carbohydrate and mineral contents of fenugreek seeds. Indian Cocoa, Arecanut and Spices J. 20 120-124. 

Mannose, the C-2 epimer of glucose (see p. 84), is an important component of glycoproteins (see p. 164). Hexokinase phosphorylates mannose, producing mannose 6-phosphate, which, in turn, is (reversibly) isomerized to fructose 6-phosphate by phosphoman-nose isomerase. [Note There is little mannose in dietary carbohydrates. Most intracellular mannose is synthesized from fructose, or is preexisting mannose produced by the degradation of structural carbohydrates and salvaged by hexokinase.]... 

Muller et al. (1994) adapted and extended the two-compartment approach. They defined four plant compartments in addition to water cellular lipids, cuticle, structural carbohydrates, and proteins. Their predictive equation is ... 

Goes, J. I., N. Handa, S. Taguchi, T. Hama, and H. Saito. 1996. Metabolism of neutral monosaccharide constituents of storage and structural carbohydrates in natural assemblages of marine phytoplankton exposed to ultraviolet radiation. Limnology and Oceanography 41 1478-1489. 

Mucopolysaccharides are some of the most common structural carbohydrates in cestodes, although little is known of their biochemistry or function. They are heteropolymers and contain amino sugars (e.g. glucosamine, galactosamine) and uronic (glucuronic, galacturonic) acids. Often, mucopolysaccharides are complexed with proteins to form mucoproteins or glycoproteins, which, as discussed in Chapter 2, are major components of... 

Carbohydrates in algae and plants are often classified based on methodological discrimination. The structural carbohydrates are not water-soluble, whereas the other types of carbohydrates are water-soluble and typically extracted by hot water. In Phaeocystis five different pools of carbohydrates can be distinguished. Like all algal and plant cells, both solitary and colonial cells produce (1) structural carbohydrates, polysaccharides that are mainly part of the cell wall, (2) mono- and oligosaccharides, which are present as intermediates in the synthesis and catabolism of cell components, and (3) intracellular storage glucan. Colonial cells of Phaeocystis excrete (4) mucopolysaccharides, heteropolysaccharides that... 

The only quantitative data available on the contribution of structural carbohydrates to Phaeocystis biomass are from a culture of Phaeocystis sp. in the stationary phase, where structural... 

Owing to the great impact that p.m.r. spectroscopy has made on structural carbohydrate chemistry, it is not feasible to discuss here all of the reports in which this technique has been used merely to confirm assigned structures. In the present Chapter, some selectivity has been exercised in favor of novel structural and conformational applications, innovative techniques, information that could not be obtained by other methods, and a fundamental understanding of the magnetic parameters of carbohydrate molecules. 

Jeffrey GA, Wood RA (1982) The crystal structure of galactaric acid (mucic acid) at -147°C an unusually dense hydrogen-bonded structure. Carbohydr Res 108 205 - 211... 

R. Takano, K. Hayashi, S. Hara, and S. Hirase, Funoran from the red seaweed, Gloiopeltis compla-nata Polysaccharides with sulphated agarose structure and their precursor structure, Carbohydr. Polym., 27 (1995) 305-311. 

R. Stenutz, P.-E. lansson, and G. Widmalm, Computer-assisted structural analysis of oligo- and polysaccharides An extension of CASPER to multibranched structures, Carbohydr. Res., 306 (1998) 11-17. 

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