In what series does fructose belong, and how is its open-chain structure represented?

Fructose belongs to the monosaccharide series, specifically as a ketohexose. In its open-chain structure, fructose is represented as a linear molecule with six carbon atoms. The open-chain form involves a ketone functional group (C=O) located within the carbon chain. The carbon atoms are sequentially numbered, and the ketone group is typically positioned at carbon 2. However, it’s important to note that fructose readily undergoes an intramolecular reaction, forming a cyclic structure through a hemiketal linkage. This cyclic structure, particularly the five-membered ring called a furanose, is a more accurate representation of fructose in physiological conditions than its open-chain form.