D(+)-Trehalose dihydrate, 100 g

Carbohydrates or Saccharides make up 50 % of the dry biomass of the earth and are therefore the most frequent class of biomolecules. Besides at least two hydroxy groups, they also have an aldehyde or a ketone group and can be subdivided according to the number of monomeric components in mono-, di-, oligo and polysaccharides.



Whereas mono-, di- and oligosaccharides are soluble in water, taste sweet and are therefore called as sugar, polysaccharides are hardly, or not at all, soluble in water and have a neutral taste.



Carbohydrates, together with fats and proteins make up a large percentage of nutrition. In addition to their central role as an energy source, they are also an important structural component especially in plants (e.g. Cellulose). Ribose, a monosaccaride with five carbons (C₅H₁₀O₅) is an essential element of coenzymes (such as ATP, FAD and NAD) and a structural component of RNA. Desoxyribose (a ribose derivative) is a structural component of DNA.

Disaccharides

Disaccharides consist of two monosaccharide units. These are interlinked covalently via a glycocide bond. The most familiar representatives are saccharose, lactose and maltose.