Furanose is a type of sugar structure that resembles a five-membered ring, containing four carbon atoms and one oxygen atom. This configuration is commonly found in certain monosaccharides, such as ribose and fructose. Furanose forms when the carbonyl group of a sugar reacts with a hydroxyl group, leading to a cyclic structure. In contrast to furanose, sugars can also exist in a six-membered ring form called pyranose. The furanose form is significant in biochemistry, as it plays a crucial role in the structure of nucleotides and nucleic acids, such as RNA. Understanding furanose is essential for studying carbohydrate chemistry and molecular biology.