The aldopentoses are a subclass of the pentoses which, in the linear form, have the carbonyl at carbon 1, forming an aldehyde derivative with structure H–C(=O)–(CHOH)4–H. The most important example is 展开

The closed or cyclic form of a pentose is created when the carbonyl group interacts with a hydroxyl in another carbon, turning the carbonyl into a hydroxyl and creating an ether bridge –O– between the two carbons. This intramolecular reaction yields a cyclic 展开

In the cell, pentoses have a higher metabolic stability than hexoses.
A polymer composed of pentose sugars is called a pentosan.
Tests for pentoses 展开