Cellulose in cell walls

The origin and function of xylan in the cell wall are also not explained. Postulations that it is a plasticizer or is a reserve food are not fully substantiated. Its derivation from cellulose through the decarboxylation of an intermediary polyglucuronic acid seems very unlikely. There is evidence from a number of sources to indicate that the xylan polysaccharide is deposited along with cellulose in cell wall elaboration. 

Heyn, A. N. J. (1966). The microcrystalline structure of cellulose in cell walls of cotton, ramie, and jute fibers as revealed by negative staining of sections./. Cell. Biol. 29 181-197. 

In both primary and secondary cell walls, cellulose is mixed with other polysaccharides (O Table 1) and lignin [20,21,22,23,24,25,26]. Historically, the other polysaccharides have been called hemicelluloses. The term hemicellulose indicates a polysaccharide closely associated with cellulose in cell walls. The relationship is physical, not stmctural. These polysaccharides are almost always heteroglycans 8-glucans and some polysaccharides that are composed almost exclusively of D-xylose are among the exceptions. Stmctures of hemicelluloses vary from linear to highly branched and bushlike. 

Cellulose is an important part of woody plants, occurring in cell walls and making up part of the structural material of stems and trunks. Cotton and flax are almost pure cellulose. Chemically, cellulose is a polysaccharide—a polymer made by successive reaction of many glucose molecules giving a high molecular weight (molecular weight ->- 600,000). This polymer is not basically different from the polymers that were discussed in Section 18-6 ... 

Biosorption is a rather complex process affected by several factors that include different binding mechanisms (Figure 10.4). Most of the functional groups responsible for metal binding are found in cell walls and include carboxyl, hydroxyl, sulfate, sulfhydryl, phosphate, amino, amide, imine, and imidazol moieties.4 90 The cell wall of plant biomass has proteins, lipids, carbohydrate polymers (cellulose, xylane, mannan, etc.), and inorganic ions of Ca(II), Mg(II), and so on. The carboxylic and phosphate groups in the cell wall are the main acidic functional groups that affect directly the adsorption capacity of the biomass.101... 

Raman microscopy cellulose microfibrils in cell walls and distinguishing crystalline and noncrystalline inclusions Analysis of bioaccumulations in plant vacuoles ... 

The polysaccharide compositions of potato cell walls have been genetically manipulated for two main reasons first to attempt to understand the functions of the different cell-wall polysaccharides, and second to improve the value of potato pulp waste. The yield of pectin extracted from the pulp would be improved by decreasing the proportion of cellulose in the walls. The gelling quality of this pectin would also probably be improved by reducing the proportion of RG-1 side chains (Sorensen et al., 2000). 

Alginates, found in cell walls of some marine algae and also formed by certain bacteria, consist in part of a linear i-l,4-linked polymer of D-mannuronate with a cellulose-like structure. Alginates also contain... 

Least Soluble Polysaccharides. As indicated, the most insoluble polysaccharides are those which are reinforcing structural polymers in cell walls. The best example is cellulose, the universal reinforcing struc-... 

Several procedures have been used to hydrolyze polysaccharides in cell walls and cell wall fractions. For example, the noncellulosic polysaccharides can be hydrolyzed using 1 M sulfuric acid for 2 to 3 hr at 100°C (Selvendran and Ryden, 1990). One of the simplest procedures is that of Albersheim et al. (1967) in which hydrolysis of the noncellulosic polysaccharides is achieved by incubating in 2 M trifluoroacetic acid (TFA) at 121 °C for 1 hr. The advantage of the TFA procedure is that it is quick and the acid can be removed by evaporation in a gentle stream of air or nitrogen. However, neither the 1 M sulfuric acid or TFA procedures hydrolyze cellulose. Hydrolysis of cellulose can be achieved by an initial dispersion in 72% (w/w) sulfuric acid (Saeman et al., 1963 Selvendran et al., 1979 Fry, 1988 Harris et al., 1988 Selvendran and Ryden, 1990) followed by hydrolysis in 1 M sulfuric acid. 

Eukaryotic cells are also characterized by one or more structures exterior to the cytoplasmic membrane. Plant cells have a rigid cellulose-containing cell wall, and animal cells have a cell coat composed of glycoproteins (contain carbohydrate) and other components that do not confine the cell but are important in cell-cell recognition. 

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