1,3-Bisphosphoglycerate (1,3BPG), also known as PGAP, is a 3-carbon organic molecule present in most, if not all, living organisms. It primarily exists as a metabolic intermediate in both glycolysis during respiration and the Calvin cycle during photosynthesis. 1,3BPG is a transitional stage between glycerate 3-phosphate and glyceraldehyde 3-phosphate during the fixation/reduction of CO₂. 1,3BPG is also a precursor to 2,3-bisphosphoglycerate which in turn is a reaction intermediate in the glycolytic pathway.1,3-bisphosphoglycerate is the anion form of bisphosphoglyceric acid. It is phosphorylated at the number 1 and 3 carbons. The result of this phosphorylation gives 1,3BPG important biological properties such as the ability to phosphorylate ADP to form the energy storage molecule ATP. As previously mentioned 1,3BPG is a metabolic intermediate in the glycolytic pathway. It is created by the exergonic oxidation of the aldehyde in G3P.