pentoosins

Pentoosins are a class of organic compounds that are polyhydroxy aldehydes or ketones containing five carbon atoms. They are a type of monosaccharide, meaning they cannot be hydrolyzed into simpler carbohydrates. The term "pentose" refers to the five-carbon structure, and the "-ose" suffix indicates they are sugars.

The two most common pentooses are ribose and deoxyribose. Ribose is a five-carbon aldose, meaning it contains an aldehyde group. It is a crucial component of RNA, ATP, and various coenzymes like NAD and FAD. Deoxyribose is similar to ribose but lacks an oxygen atom on the second carbon. It is the fundamental building block of DNA. Other important pentooses include arabinose, xylose, and ribulose, which play roles in plant cell walls, metabolism, and photosynthesis, respectively.

Pentoosins exist in both open-chain and cyclic forms. The cyclic forms, furanoses, are more stable and prevalent in biological systems. These cyclic structures involve the formation of a five-membered ring. The presence and arrangement of hydroxyl groups on the carbon chain define the specific stereoisomer of a pentoose. While they are carbohydrates, pentooses are often less sweet than hexoses (six-carbon sugars) and can be metabolized through different pathways.