Ketohexózy

Ketohexózy are a class of carbohydrates that are monosaccharides containing six carbon atoms and a ketone functional group. They are also known as ketohexoses. The most common ketohexose is fructose, which is a simple sugar found in fruits and honey. Another example is sedoheptulose, a seven-carbon sugar, though it is not a hexose. Ketohexoses have the general chemical formula C6H12O6, the same as aldohexoses.

The structure of a ketohexose features a carbonyl group (C=O) on the second carbon atom. This differs from aldohexoses, which have a carbonyl group on the first carbon atom. Ketohexoses exist in both open-chain and cyclic forms. The cyclic forms are typically furanose rings, which are five-membered rings, or pyranose rings, which are six-membered rings. Fructose, for instance, readily interconverts between its open-chain form and cyclic furanose and pyranose forms.

In biological systems, ketohexoses play important roles. Fructose is a significant component of sucrose (table sugar) and is metabolized in the liver. While fructose is a natural sweetener, excessive intake has been linked to metabolic issues. Ketohexoses are involved in various metabolic pathways, including glycolysis, though they enter this pathway differently than aldohexoses. Their presence and metabolism are crucial for energy production in many organisms.