Polyuronides pectic

We also lack any knowledge of the ultimate fate of pectic substances and galacturonic add in plant tissues. Little proof exists whether pectic substances may or may not serve as reserve carbohydrates that can be metabolized by the cell. From the fragmentary information on hand, it is not even certain that these pol mronides, once formed, actually disappear from the tissue. The decreasing proportion of pectin in a tissue can be often explained by dilution with newly formed constituents and higher proportion of waterSuch retention of the pectic polyuronides by the tissue would be in harmony with their known structural function. 

Most of the cells of wood are long, narrow hollow fibers and tubular-shaped cells arranged with their long axes parallel to the axis of the tree trunk. Certain food storage cells lie in radial bands, termed wood rays, which are perpendicular to the tree axis. The walls of this complex system of plant cells form the basic framework and material of all wood substance, All wood substance is composed of two basic chemical materials, lignin, and a polysaccharidic system, which is termed holoceliulose. The latter embraces cellulose and the hemicelluloses, a mixture of pentosans, hexosans and polyuronides, and in some instances small amounts of pectic materials. Wood cell wall tissue also always retains small amounts of mineral matter (ash). 

Polyuronides may be defined as polysaccharides that contain one or more uronic acid units in their molecular structures. They have a frequent and wide occurrence in nature. Much of the carbohydrate material in plants belongs to the group. It includes all pectic materials and plant gums and many plant mucilages, hemicelluloses and gel-forming substances and some microbial polysaccharides. These substances are to be looked for in water-soluble plant exudates and mucilages, as well as in water and alkaline extracts of most plant materials. This review will be limited to the polyuronides occurring in plants. 

Physical Methods. Infrared (IR), Raman, and nuclear magnetic resonance (NMR) spectroscopic methods have been applied to structural analysis of polysaccharides such as pectin. These applications have been reviewed ( ), and reference IR spectra of pectic substances have been published ( ). Quantitative IR has been used to estimate acid dissociation constants of polyuronides from the ratio of -CO2H to -CO2- as a function of pH ( ). Also, by... 

Polyuronides are a major component of the primary cell wall and middle lamella of higher plant cortical tissues (1, 2). These polymers are efficient cation exchangers (3, 4) and, thus, can affect ion activity, transmembrane potential and electrolyte flux (5). In addition, the divalent salts of pectic substances... 

Polyuronides Partially dicarboxylated pectic acid Mn = 11,900 67% carboxylated Biological oxygen demand Activated sludge [144]... 

The various groups of pectic substances are usually characterized by their solubility behavior. Polygalacturonides, like other polyuronides, can be quantitatively estimated by the amount of carbon dioxide formed upon heating with hot acid. Pectic substances of all sorts have been commonly determined by the formation and weighing of water-insoluble pectic acid or calcium pectate but unfortunately it is difficult to get these precipitates free from impurities (particularly other polysaccharides) present in the material analyzed. Today, the most common method of estimation is the spectrophotometric measurement of the colored complex formed upon the addition of alcoholic carbazole to the material to be analyzed after alkali treatment and heating with concentrated sulfuric acid. ... 

It is generally known that polyuronides (alginates and pectic substances) are natural ion exchangers of outstanding properties. Alginate occurs in the cell wall and intracellular spaces of brown algae [62]. It is an unbranched... 

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