Polymerization, glucose

Glucose polymerizes to form glycogen when the organism has no immediate need for the enei derived from glucose breakdown. 

Work by Rees (3) shows the various geometries of the monomer linkages for the poTypyranosides. When glucose polymerizes. Cl is always involved, and the linkage is to the 02, 03, 04 or 06 of the adjacent monomer. The relative angles of the Cl-01 bond with the Cn-On bond in the same monomeric unit determine a catagory of shapes that the polymer can acquire. 

Pathways and mechanisms of uridine diphosphoglucose (UDP-Glucose) synthesis are relatively well known, whereas molecular mechanisms of glucose polymerization into long and unbranched chains still need exploring. 

The concentration of primer, while not influencing the amount of glucose polymerized, does determine the average chain length of the product. Muscle phosphorylase was isolated in two crystalline forms, a and... 

Cellulose and amylose are comprised of the same glucose subunits as the cyclodexttins. In the case of cellulose, the glucose units are attached through 1,4-P-linkages resulting ia a linear polymer. In the case of amylose, the 1,4-a-linkages, as are found ia the cyclodexttins, are thought to confer heUcity to the polymeric chain. 

Polymeric cation-exchange resins are also used in the separation of fmctose from glucose. The UOP Sarex process has employed both 2eohtic and polymeric resin adsorbents for the production of high fmctose com symp (HFCS). The operating characteristics of these two adsorbents are substantially different and have been compared in terms of fundamental characteristics such as capacity, selectivity, and adsorption kinetics (51). 

Polydextrose (Pfizer) is prepared by high temperature polymerization of glucose in the presence of a catalyst. It is a water-soluble, amorphous soUd used primarily as a hulking agent (52). Dried fmit, including pmnes, and dried plum, date, and grape juice is used for similar appUcations (53). 

Dextrose (D-glucose) is by far the most abundant sugar in nature. It occurs either in the monosaccharide form (free state) or in a polymeric form of anhydrodextrose units. As a monosaccharide, dextrose is present in substantial quantities in honey, fmits, and berries. As a polymer, dextrose occurs in starch, cellulose (qv), and glycogen. Sucrose is a disaccharide of dextrose and fmctose. 

Cellulose is the main component of the wood cell wall, typically 40—50% by weight of the dry wood. Pure cellulose is a polymer of glucose residues joined by 1,4-P-glucosidic bonds. The degree of polymerization (DP) is variable and may range from 700 to 10,000 DP or more. Wood cellulose is more resistant to dilute acid hydrolysis than hemiceUulose. X-ray diffraction indicates a partial crystalline stmcture for wood cellulose. The crystalline regions are more difficult to hydrolyze than the amorphous regions because removal of the easily hydrolyzed material has Htde effect on the diffraction pattern. 

Starch A polymeric substance of glucose molecules and a component of many terrestrial and aquatic plants used by some organisms as a means of energy storage starch is broken down by enzymes (amylases) to yield glucose, which can be used as a feedstock for chemical or energy production. 

The selective separation range of the S-500/S 1000-system for glucans is shown for hybrid starch Triticale T22. This mixture of scb and nb/lcb glucans contains components in the range between approximately dp 50-300,000 glucose monomers (Fig. 16.11). The degree of polymerization distribution obtained from dextran-based calibration was computed as well in terms of... 

FIGURE 16.13 Degree of polymerization distribution (m dpD d) for synthesized amylose -type nb/lcb glucans calculated from dextran-calibrated — amylose-converted calibration of S-SOO/S-IOOO dp. = SSI [glucose units]. 

Briefly summarized, S-1000 shows better resolution in the high dp range, whereas the CL 2B system resolves low dp components better. Due to these differences in separation performance, the degree of polymerization distribution and degree of polymerization average values for the same sample obtained from broad scb— nb/lcb-transformed dextran calibration yielded dp = 29,900 glucose units for the S-1000 system and dp = 21,100 glucose units for the CL 2B system (Fig. 16.18). 

Figure I 6.34 Degree of polymerization distribution molar distribution ( ) with number average degree of polymerization (dp = 140 glucose unimers) mass distribution ( ) with weight average degree of polymerization dp = 1242 glucose unimers.

Chemical Name Polymeric glucose (see structural formula) of molecular weight 40,000 Common Name —... 

Carbohydrates include sugars, starches, and cellulose. Glucose is an alcohol and an aldehyde that polymerizes to form starch and cellulose. 

Amylopectin is the polymeric component of starch and consists mainly of glucose units joined at the 1,4-positions. Relative molar mass tends to be very high, e.g. between 7 and 70 million. A variety of modified starches are used commercially which are produced by derivatisation to give materials such as ethanoates (acetates), phosphates, and hydroxyalkyl ethers. Modified and unmodified starches are used in approximately equal tonnages, mainly in papermaking, paper coatings, paper adhesives, textile sizes, and food thickeners. 

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