Biochemical Engineering Fundamentals, Part 1 - Bailey J., Ollis D. 1989

Chemical Foundations of Life
Sugars and Polysaccharides
D-Glucose and Other Monosaccharides

Monosaccharides, or simple sugars, are the simplest CARBOHYDRATES. They contain from three to nine carbon atoms and serve as monomeric units in the synthesis of non-genetic Biopolymers with molecular masses of up to several million.

Glucose, like Other simple sugars, is a polyhydroxy hydrocarbon derivative (Table 2.2) and always occurs in natural sources as D-(+)-glucose, i.e., as the optical isomer that rotates the plane of polarized light to the right.

Although D-glucose is by far the most abundant monosaccharide, other simple sugars also occur in living organisms (Table 2.2). They all contain either an aldehyde or a ketone group. In naming sugars, The Nature of this group is usually indicated first, followed by the number of carbon atoms in the chain. Thus, for example, glucose is called an aldohexose; the symbol D denotes a specific optical isomer, the form in which this monosaccharide is almost always present in living systems (for optical activity, see Section 2.4).

In solution, D-glucose exists mainly as a cyclic compound, a so-called pyranose, formed by the reaction of the C-1 aldehyde group with the hydroxyl group at C-5 (note the standard numbering system for the six carbon atoms, as well as the symbols α and β, which designate the spatial orientation of the hydroxyl group at C-1).

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The five-membered sugars D-ribose and deoxyribose are Key Components of the monomeric units of Nucleic Acids (DNA and RNA) and other biologically important compounds, which we will briefly discuss later.