Pentose Cycle
(Pentose phosphate pathway)

This cycle is called pentose cycle because phosphorylated pentose’s (in particular ribose-5-phosphate) play an important role. This metabolic pathway is a complicated branch of the glycolysis and is active in the cytoplasm of the cell. This cycle becomes active when NADPH and/or ribose-5-phosphate are needed. NADPH is needed in the cells for the biosynthesis (to produces new molecules). NADPH functions as an electron donor (H-, =energy). Ribose-5-phosphate is needed for the formation of for example: ATP, CoA, NAD, FAD, RNA and DNA.
Other functions of the pentose cycle are the (non-oxidative) mutual transformation of 3, 4, 5 and 6 sugars.

The pentose cycle in reactions

The pentose cycle in chemical formulas

The pentose cycle in reactions

                                          Glucose

                                   Glucose 6-phosphate            6-phosphogluconolactone

                                                                                                                      6-phosphogluconate

                                Fructose 6-phosphate                                                          Ribulose-5-phosphate


                             Fructose 1,6-disphosphate                                  Xylulose-5-phosphate             Ribose-5-phosphate

                         Fructose-6-P + Glyceraldehyd-3-P                            Glyceraldehyd-3-phosphate + Sedulhepulose-7-phosphate

                                                                                                 Erythrose-4-phosphate + Fructose 6-phosphate