What is the basic formula for monosaccharides and how is the shape determined?

Monosaccharides are simple sugars with a basic formula Cⁿ (H2O) ⁿ. They are classified according to the number of carbon atoms they contain: tetroses (4), pentoses (5) and hexoses (6). There are also mosaccharides with 3 carbon atoms, for example the Dihydroxyacetone.

Explanation:

Monosaccharides have to be aldehydes (-CHO) or ketones (-COO) with more than one alcohol function, which will be located in different carbons.

Therefore, the molecular structure of a simple monosaccharide can be written as H (CHOH) n (C=O) (CHOH) mH, where n + 1 + m = x; so that its elemental formula is CxH2xOx. By convention, the carbon atoms are numbered from 1 to x along the backbone, starting from the end that is closest to the C=O group.