Carbohydrate importance

Sugar Alcohols. These are polyols, chemically reduced carbohydrates. Important in this group are sorbitol, mannitol, maltitol, and xylitol. Xylitol is described later. 

How are carbohydrates important in the immune response In glycoproteins, carbohydrate residues are covalently linked to the polypeptide chain. Such glycoproteins can play a role in the recognition sites of antigens. A common example is the ABO blood group, in which the three major blood types are distinguished by sugar molecules attached to the protein. 

Lectins (from latin legere=to choose). Term for certain proteins or glycoproteins which specifrcally recognize and bind to (poly)saccharides which may even be bound to lipids or carbohydrates. Important examples are abrin, concanavalin A, ricin and phasin. L. are abundant in most organisms, very high contents are found in beans and slugs. The Mr of L. ranges from... 

Found in many plant gums in polymeric combination with other carbohydrates. Important structural constituent of practically all fibrous and connective tissues in the animal organism. Readily obt. from glucose. Inexpensive starting material for synthesis. 

Carbohydrates may be divided into monosaccharides, disaccharides and polysaccharides. The monosaccharides under certain conditions react as polyhydroxy-aldehydes or polyhydroxy-ketones two important representatives are glucose CjHjjO (an aldose) and fructose (laevulose) CgHuO, (a ketose). Upon hydrolysis di- and polysaccharides 3deld ultimately monosaccharides. Common disaccharides are sucrose, lactose and maltose (all of molecular formula C,2H2. 0,), whilst starch, dextrin and cellulose, (CjHjoOj), in which n > 4, are typical polysaccharides. 

Typical carbon-oxygen bond distances m ethers are similar to those of alcohols (—142 pm) and are shorter than carbon-carbon bond distances m alkanes (—153 pm) An ether oxygen affects the conformation of a molecule m much the same way that a CH2 unit does The most stable conformation of diethyl ether is the all staggered anti conformation Tetrahydropyran is most stable m the chair conformation—a fact that has an important bearing on the structures of many carbohydrates... 

Of all the monosaccharides d (+) glucose is the best known most important and most abundant Its formation from carbon dioxide water and sunlight is the central theme of photosynthesis Carbohydrate formation by photosynthesis is estimated to be on the order of 10 tons per year a source of stored energy utilized directly or indi rectly by all higher forms of life on the planet Glucose was isolated from raisins m 1747 and by hydrolysis of starch m 1811 Its structure was determined in work culmi nating m 1900 by Emil Fischer... 

Glycosides are a large and very important class of carbohydrate derivatives character ized by the replacement of the anomeric hydroxyl group by some other substituent Gly cosides are termed O glycosides N glycosides S glycosides and so on according to the atom attached to the anomeric carbon... 

Corticosteroids exhibit a wide range of physiological effects One important func tion IS to assist m maintaining the proper electrolyte balance m body fluids They also play a vital regulatory role m the metabolism of carbohydrates and m mediating the alter gic response... 

The most important derivatives of pyrimidines and purines are nucleosides Nucleosides are N glycosides m which a pyrimidine or purine nitrogen is bonded to the anomeric carbon of a carbohydrate The nucleosides listed m Table 28 2 are the mam building blocks of nucleic acids In RNA the carbohydrate component is d ribofuranose m DNA It IS 2 deoxy d ribofuranose... 

Section 28 2 Nucleosides are carbohydrate derivatives of pyrimidine and purine bases The most important nucleosides are derived from d ribose and 2 deoxy D ribose... 

Biochemistry resulted from the early elucidation of the pathway of enzymatic conversion of glucose to ethanol by yeasts and its relation to carbohydrate metaboHsm in animals. The word enzyme means "in yeast," and the earfler word ferment has an obvious connection. Partly because of the importance of wine and related products and partly because yeasts are relatively easily studied, yeasts and fermentation were important in early scientific development and stiU figure widely in studies of biochemical mechanisms, genetic control, cell characteristics, etc. Fermentation yeast was the first eukaryote to have its genome elucidated. 

Lubricity appears to be easier to measure and to replace in lower fat foods. Carbohydrates and particulated proteins can be formulated so that they help in this important aspect of fats. 

Spices and herbs can play an important indirect role in good nutrition. They are not high in nutrient values, but they help to increase the appeal and satisfaction of foods that are highly nutritious. Spices do contain fat, protein and carbohydrates, electrolytic minerals, iron and B vitamins, and others, but even the highest calorie spice, poppy seeds, contains only two to three calories per serving in normal use (12). 

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