noun, plural: carbohydrates
Any of the group of organic compounds consisting of carbon, hydrogen, and oxygen, usually in the ratio of 1:2:1, hence the general formula: Cn (H2O) n. Examples include sugar, starch, cellulose and gums.
Carbohydrates are the most abundant among the major classes of biomolecules. Chemically, they are simple organic compounds that are aldehydes or ketones with many hydroxyl groups added usually on each carbon atom not part of the aldehyde or ketone functional group.
Most of the carbohydrates follow the general formula: Cn (H2O) n, from where they derive their name, which means hydrates of carbon. However, not all carbohydrates follow this formula and are slightly different in structure from this rule. Moreover, there are some compounds that seem to follow this rule but are not carbohydrates (e.g. formaldehyde).
Carbohydrates may be classified into monosaccharides, disaccharides, oligosaccharides, polysaccharides, and heterosaccharides. The most fundamental type is the simple sugars called monosaccharides, such as glucose, galactose, and fructose. These simple sugars can combine with each other to form more complex types. The combination of two simple sugars is called disaccharide whereas carbohydrates consisting of two to ten simple sugars are called oligosaccharides, and those with a larger number are called polysaccharides.
Carbohydrates are produced in green plants by photosynthesis and serve as a major source of energy in animal diets. They also serve as structural components, such as cellulose in plants and chitin in some animals. Their derivatives play an essential role in the working process of the immune system, fertilization, pathogenesis, blood clotting and development.
More info relating to carbohydrates and their role in our diet can be found in the developmental biology tutorial investigating a balanced diet.