monosaccharider

Monosaccharider, also known as monosaccharides, are the simplest carbohydrates and the fundamental building blocks of more complex carbohydrates. They are polyhydroxy aldehydes or ketones that cannot be hydrolyzed into smaller sugar units. Most have the empirical formula (CH2O)n with n typically between 3 and 7, and they exist in linear and cyclic forms in solution. In water, many sugars form ring structures such as pyranoses (six-membered rings) and furanoses (five-membered rings).

Monosaccharider are classified by functional group as aldoses (aldehyde group) or ketoses (ketone group), and by chain length as triose, tetrose, pentose, hexose, or heptose. Common examples include glucose (an aldohexose), galactose and mannose; fructose (a ketohexose); ribose and deoxyribose (pentoses inhabiting nucleic acids). In biology, most dietary sugars are D-enantiomers; L forms are rare.

They are highly soluble in water and have a sweet taste; many are reducing sugars because they possess a free carbonyl group that can be oxidized. They serve as energy sources and as monomers for disaccharides (such as sucrose, lactose, maltose) and polysaccharides (starch, glycogen, cellulose). They are also key components of nucleic acids (ribose, deoxyribose) and participate in metabolic pathways such as glycolysis and the pentose phosphate pathway, as well as in sugar transport.