Carbohydrates are substances composed mainly of carbon, hydrogen and oxygen.

Carbohydrates , also known as carbohydrates or sugars, are important biomolecules that form the basis of nutrition for non-photosynthetic organisms. They can be defined as polyhydroxyaldehydes or polyhydroxyketones or substances that release these compounds when they undergo the process of hydrolysis (breakdown of a molecule by water).

Carbohydrates are the most prevalent biomolecules on the planet and perform the most varied functions. Among them, its energetic role, its performance in the composition of nucleic acids, cell walls and insect carapace, and its participation in cell-cell interaction processes stand out.

Carbohydrates are formed mainly by carbon, hydrogen and oxygen, with the following general formula: (CH 2 O) n . Thanks to this formula, they are also called carbohydrates. It is worth noting that some carbohydrates deviate from the general formula and have nitrogen, phosphorus or sulfur in their composition.

We can classify carbohydrates into three main groups:

→ Monosaccharides: These are the simplest compounds that cannot be hydrolyzed. Its structure is a straight and simple carbon chain. As an example, we can mention glucose, fructose and galactose.

Monosaccharides can be classified according to the number of carbons they contain. According to this classification, there are trioses, tetroses, pentoses, hexoses, heptoses, and so on. The most common monosaccharides are pentoses, such as ribose and deoxyribose, and hexoses, which can be represented by glucose, fructose and galactose.

→ Polysaccharides: They are formed by 10 or more monosaccharides. As an example, we can mention starch, glycogen and cellulose, three important macromolecules. Starch is an important energy reserve found in plants and fungi. The energy reserve found in animals is glycogen , which is accumulated in the liver and muscles. Cellulose is an important component of the cell wall , being the most abundant carbohydrate in nature.

There are also the so-called glycoconjugates , which are compounds formed by the binding of carbohydrate molecules to lipids and proteins. When attached to proteins , they are called glycoproteins; and when they bind to lipids , they are called glycolipids . These forms are quite common in cell membranes where they act as receptors and signalers. 

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