Carbohydrates (general characteristics)

Carbohydrates, also referred to as sugars, are a class of biomolecules characterized by the presence of many polar groups in its composition. The building block of the carbohydrates are the monosaccharides, since any carbohydrate has one, or more than one, monosaccharide. Consequently, they can be grouped into different classes, namely, monosaccharides, oligosaccharides and polysaccharides.

When only one or a few monosaccharides are present, usually the carbohydrate has a sweet taste and is therefore referred to as sugars. In fact, when looking for a label of a food product, it is common an information like "Carbohydrates of which sugars". This information may cause some confusion, because in fact there is some ambiguity in the designation of sugar. If some people call sugars to carbohydrates, there are those who use this designation only to carbohydrates that are sweet.
Carbohydrates are the most abundant class of biomolecules in nature, being also the most abundant class of biomolecules in our food, and should correspond to 45-75% of total energy intake.
Carbohydrates exist in a free form, i.e. without being linked to other types of molecules. In this case, they are referred to as poly-hydroxyaldehydes or poly-hydroxyketones, since they present several hydroxyl groups and one carbonyl group which can be aldehyde or ketone, respectively (if you have any questions about these functional groups, you can find more information about them HERE and HERE). 

If carbohydrates are combined with other molecules, the resulting molecule is referred to as a glycoconjugate, being the most well-known glycoconjugates the glycoproteins and glycolipids.

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