Monosaccharides or oses are the simplest carbohydrates and cannot be hydrolysed. There are two types: aldoses and cetoses.
They are distinguished by the number of carbon atoms in their chemical structure: such as trioses, pentoses, and hexoses. The main monosaccharides are glucose, fructose and mannose. They all have the same chemical formula (Cn(H2O)n), although have different configurations.
Structure of the most common oses (monosaccharides) © Boumphreyfr, Wikimedia CC by-sa 3.0