Sucrose digestion

D-Fructose in the human diet derives mainly from sucrose, fruits, and honey. Sucrose is /I-D-fructofuranosyl a-D-glucopyranoside, and, after hydrolysis by invertase (EC 3.2.1.26), to D-glucose and D-fructose, can be absorbed from the small intestine. In the human intestine, invertase, as well as a-D-glucosidases, is developed very early in fetal life, and even appears much earlier than lactase (EC 3.2.1.23). There is no significant, intestinal transport of unhydrolyzed sucrose, and, in animal experiments, sucrose administered by injection is quantitatively excreted in the urine.1 Intestinal invertase is produced by mucosal cells localized in the brush-border membrane of the mucosal epithelia. Invertase is not secreted,1-4 and little or no invertase (sucrase) has been found in the intestinal lumen.1 The specific localization of sucrase at the mucosal, luminal interface is thought to be of functional importance in coupling sucrose digestion to transport.1... 

Sucrose polyesters, which are made by esterilying sucrose with long-chain fatty acids, have the physical properties of fat, but are resistant to digestive enzymes (40). Olestra, a sucrose polyester developed by Procter Gamble, was submitted for regulatory approval in May 1987. In order to faciUtate the approval process, Procter Gamble has since narrowed the scope of its food additive petition to include olestra s use only in savory and extmded snacks. 

Acarbose is a nonabsorbable a-glucosidase inhibitor which blocks the digestion of starch, sucrose, and maltose. The digestion of complex carbohydrates is delayed and occurs throughout the small intestine rather than in the upper part of the jejunum. Absorption of glucose and other monosaccharides is not affected. Acarbose is adrninistered orally three times a day and chewed with the first mouthful of food. 

In the body, this reaction is reversed by the enzyme sucrase. This occurs in digestion, which makes glucose and fructose available for absorption into the blood. Honey bees also carry an enzyme that can hydrolyze sucrose. Honey consists mostly of a 1 1 mol mixture of glucose and fructose with a small amount of unreacted sucrose. 

Olestra is a nondigestible plastic, made by adding eight fatty acid molecules to the sugar molecule sucrose. The fatty acids block access to the sugar, so enzymes can t break it down. The result is a molecule that behaves like a fat, but cannot be digested by humans. 

The hydrolysis of sucrose is a part of the digestive process. To investigate how strongly the rate depends on our body temperature, calculate the rate constant for the hydrolysis of sucrose at 35.0°C, given that k = 1.0 mL-mol -s 1 at 37.0°C (normal body temperature) and that the activation energy of the reaction is 108 kj-mol. ... 

Protoplasmic structures are not very stable. Consequently, if protective agents were not employed, destruction of the walls was accompanied by a rapid lysis of the protoplasts, followed by the liberation of most of the cell protein and nucleic acid in soluble form. This could be prevented by employment of the enzyme in a 0.2 M solution of sucrose or cane sugar. After digestion of the cell walls, the living protoplasts rounded up into spheres. 

Variations Other protocols use high-salt solutions in combination with isopropanol to precipitate RNA from sucrose fractions. Standard proteinase K digestion in the presence of SDS may be used to extract RNA from the precipitated material. 

Santini, R., Jr., Perez-Santiago, E., Martinez de Jesus, J., and Butterworth, C. E., Jr., Evidence of increased intestinal absorption of molecular sucrose in sprue. Am. ]. Digest. Diseases 2, 683-668 (1957). 

The nucleosome is composed of 200 base pairs of DNA and an octamer of the histones H2A, H2B, H3, and H4 as well as histone HI (Komberg, 1974, 1977). Nucleosomes can be obtained by mild digestion of chromatin with micrococcal nuclease (Noll, 1974a Axel, 1975), followed by fractionation on a sucrose gradient. Further digestion of the nucleosomes results in the formation of nucleosome core particles composed of 145 base pairs of DNA and an octamer of the histones H2A, H2B, H3, and H4 (Rill and Van Holde, 1973 Sollner-Webb and Felsenfeld, 1975 Axel, 1975 Bakayev et al., 1975 Whitlock and Simpson, 1976 Noll and Komberg, 1977). The DNA piece thus excised is called linker DNA which serves as a link... 

Digestion of starch involves the hydrolysis of the bonds between the glucose molecules. Two classes of hydrolytic enzymes are required amylases and oligo- and di-saccharidases (Figure 4.5). The disaccharidases are also involved in hydrolysis of sucrose and lactose. 

DNA methylation induced chromatin fiber compaction only in the presence of bound LH AFM results substantiated by MNase digestion patterns and sucrose gradient centrifugation ... 

Acarbose is an intestinal a-glucosidase inhibitor that delays digestion and absorption of starch and sucrose. It is used in diabetes mellitus and is contraindicated in inflammatory bowel disease. 

No-calories fat substitutes, such as sucrose polyesters (Olestra), which are synthesized from sucrose and fatty acid methyl esters, have been widely studied and several snacks fried in this medium are available in the market place. This product has no calories since digestive enzymes are not able to break it down due to structural impairment. A major disadvantage that prevents a wide acceptance of this product is related to the gastrointestinal discomfort that may be caused to some individuals (Dobraszczyk et ah, 2006, p. 104). 

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