Ketose

A ketose is a monosaccharide whose open-chain form contains a ketone group. In water, it commonly exists in cyclic forms produced by intramolecular reaction of that carbonyl group.

Monosaccharide: A simple carbohydrate that cannot be hydrolyzed into smaller carbohydrates. Ketoses are classified as monosaccharides by their inability to yield smaller sugars through hydrolysis.
Hemiketal: A compound in which one carbon bears both a hydroxyl group and an alkoxy group, formed from a ketone and an alcohol. Ketose ring closure converts its ketone carbonyl into a hemiketal.
Fructose: A six-carbon ketohexose found in fruits, honey, and many biological pathways. Fructose is the best-known dietary ketose and a common example of a ketohexose.
Glycolysis: A metabolic pathway that converts glucose into pyruvate while producing ATP and NADH. Ketose intermediates, including fructose 1,6-bisphosphate, are central to glycolysis.
Ketone: An organic compound containing a carbonyl group bonded to two carbon atoms. A ketone carbonyl in the open-chain structure is the defining feature of a ketose.
Furanose: A cyclic sugar form with a five-membered ring containing one oxygen atom. Many ketoses cyclize into five-membered furanose rings.
Ribulose: A five-carbon ketopentose that occurs in central metabolic pathways. Ribulose demonstrates the role of ketopentoses in carbon metabolism.
Pentose phosphate pathway: A metabolic pathway that produces NADPH and pentose sugars from glucose 6-phosphate. The pathway forms and consumes ketopentoses such as ribulose 5-phosphate and xylulose 5-phosphate.
Aldose: A monosaccharide whose open-chain form contains an aldehyde group. Aldoses differ from ketoses by the position and type of their open-chain carbonyl group.
Pyranose: A cyclic sugar form with a six-membered ring containing one oxygen atom. Some ketoses form six-membered pyranose rings, alongside their other solution forms.

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