A five-carbon sugar in which carbons 2, 3, or 4 make up part of a carbonyl group; e.g., ribulose. ... (05 Mar 2000) ... 
Type: Term Pronunciation: kē′tō-pen′tōs Definitions: 1. A five-carbon sugar in which carbons 2, 3, or 4 make up part of a carbonyl group, ribulose.