Pentose Phosphate Pathway or HMP Pathway

In microbes (bacteria and some fungi) used for Industrial production of commercial products such as antibiotics and in highly metabolically active tissues of animals, most efficient respiratory pathway has been discovered. It is called PPP or Pentose Phosphate Pathway or Hexose-Monophosphate Shunt Pathway or Direct Oxidation of Glucose-pathway. The site of this respiratory pathway is cytosol and it does not require ETC (electron transport chain) or the mitochondrion.

It this pathway, when a molecule of glucose enters the respiratory process, it is phosphorylated to Glucose-6-Phosphate by consumption of one ATP-molecule. This Glucose-6-P molecule, meets a group of 5 glucose-6-P molecules in the cytoplasm, which in the presence of dehydrogenase and 6 NADP get oxidized to 6 Phosphoglucomutase molecules, producing 6 NADPH₂ molecules.

In the next reaction catalyzed by dehydrogenase and decarboxylase, six-phosphogluconate molecules, get oxidised to six molecules of pentose sugar, Ribulose-5P; producing 6 CO₂ (that diffuse in air) and 6 more NADP get reduced to 6 NADPH₂.