Monosaccharides, the simplest form of carbohydrates, contain two primary functional groups: aldehyde and ketone groups. These functional groups are crucial for the structure and reactivity of monosaccharides.
Aldoses, which are monosaccharides with an aldehyde group at one end of the molecule, include sugars like glucose and galactose. On the other hand, ketoses have a ketone group typically located at the second carbon atom; an example of this is fructose. Despite their structural differences, both functional groups play a significant role in the biological activities of these sugars.
In aqueous solutions, monosaccharides can exist in cyclic forms, wherein the aldehyde or ketone groups react with a hydroxyl group, leading to the formation of hemiacetals or hemiketals, respectively. This cyclization is crucial as it influences the reactivity and properties of sugars in various biochemical processes.