核酮糖（英语：ribulose）按结构上分类属于戊糖与酮糖。其所对应的醛糖是核糖，核酮糖的衍生物核酮糖-5-磷酸以及核酮糖-1,5-二磷酸在植物光合作用的按反应中占有重要地位。

果聚糖： 菊粉 · 果聚糖β2→6

甘露聚糖

半乳聚糖

Ribulose is a ketopentose — a monosaccharide containing five carbon atoms, and including a ketone functional group. It has chemical formula C₅H₁₀O₅. Two enantiomers are possible, D-ribulose (D-erythro-pentulose) and L-ribulose (L-erythro-pentulose). D-Ribulose is the diastereomer of D-xylulose.