Ribulose-1,5-bisphosphate (RuBP) is an organic substance that is involved in photosynthesis

Photosynthesis

Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...

. The anion is a double phosphate ester of the ketose (ketone-containing sugar) called ribulose

Ribulose

Ribulose is a ketopentose — a monosaccharide containing five carbon atoms, and including a ketone functional group. It has chemical formula 5105. Two enantiomers are possible, D-ribulose and L-ribulose . D-Ribulose is the diastereomer of D-xylulose.Ribulose sugars are composed in the...

. Salts of this species can be isolated, but its crucial biological function involves this colourless anion in solution. To simplify the presentation, the image in the above table depicts the acid form of this anion.
The enzyme ribulose bisphosphate carboxylase oxygenase (RuBisCO

RuBisCO

Ribulose-1,5-bisphosphate carboxylase oxygenase, commonly known by the shorter name RuBisCO, is an enzyme involved in the first major step of carbon fixation, a process by which atmospheric carbon dioxide is converted by plants to energy-rich molecules such as glucose. RuBisCo is an abbreviation...

) catalyzes the reaction between RuBP with carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

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