Mindblown: a blog about philosophy.

The study of polysaccharide structure usually focuses on the chemical composition, the linkage between the monosaccharide units, and the size and shape of the molecule. The size and shape of a polysaccharide can be ascertained by techniques that are usually applied to large molecules; e.g., the most accurate molecular weight determination measures the sedimentation properties of the molecule in an applied gravitational field (e.g.,…

Several other optical techniques used in chemistry have been applied to the analysis of carbohydrates. Infrared spectroscopy, used to measure vibrational and rotational excitation of molecules, and nuclear magnetic-resonance spectroscopy, which measures the excitation of certain components of molecules in a magnetic field induced by radio-frequency radiation, are valuable, although the similarity of the functional groups (i.e., the hydroxyl groups) limits use of…

A variety of organic chemical analytical techniques are generally applicable to studies involving carbohydrates. Optical rotation, for example, once was frequently used to characterize carbohydrates. The ability to measure the rotation of the plane of polarized light transmitted through a solution containing a carbohydrate depends on finding a suitable solvent; water usually is used, with light at a wavelength of 589…

In general, monosaccharides are prepared by breakdown with acids of the polysaccharides in which they occur. Sugars usually are difficult to obtain in crystalline form, and the crystallization process usually is begun by “seeding” a concentrated solution of the sugar with crystals. The techniques employed for separation of monosaccharides depend to some extent on their physical and chemical properties;…

In general, heteropolysaccharides (heteroglycans) contain two or more different monosaccharide units. Although a few representatives contain three or more different monosaccharides, most naturally occurring heteroglycans contain only two different ones and are closely associated with lipid or protein. The complex nature of these substances has made detailed structural studies extremely difficult. The major heteropolysaccharides include the connective-tissue polysaccharides, the blood group substances,…

In general, homopolysaccharides have a well-defined chemical structure, although the molecular weight of an individual amylose or xylan molecule may vary within a particular range, depending on the source; molecules from a single source also may vary in size, because most polysaccharides are formed biologically by an enzyme-catalyzed process lacking genetic information regarding size. The basic structural component of…

Polysaccharides, or glycans, may be classified in a number of ways; the following scheme is frequently used. Homopolysaccharides are defined as polysaccharides formed from only one type of monosaccharide. Homopolysaccharides may be further subdivided into straight-chain and branched-chain representatives, depending upon the arrangement of the monosaccharide units. Heteropolysaccharides are defined as polysaccharides containing two or more…

Lactose is one of the sugars (sucrose is another) found most commonly in human diets throughout the world; it constitutes about 7 percent of human milk and about 4–5 percent of the milk of mammals such as cows, goats, and sheep. Lactose consists of two aldohexoses—β-D-galactose and glucose—linked so that the aldehyde group at the anomeric carbon of glucose is…