Cyclic Photophosphorylation vs Non-cyclic Photophosphorylation
(Similarities and Differences between Cyclic and Non-cyclic Photophosphorylation)
The process of photosynthesis is completed in two main steps – Light reaction and Dark reaction. The Light reaction is the light-dependent reaction where the assimilatory powers (ATP and reduced coenzymes) are generated in the grana of chloroplasts. During the light reaction, photolysis of water and evolution of oxygen take place. In the dark reaction (light independent reaction), the assimilatory powers synthesized in the light reaction are utilized to reduce the CO2 to carbohydrates.
During the light reaction, energy in the sunlight is captured by the reaction centers of photosystems (PS I and/or PS II) and they expel electrons with high energy. These electrons then pass through a series of complexes called Electron Transport System (ETS) to synthesize the assimilatory powers. During the pathway of electrons through the ETS, phosphorylation reaction occurs at specific points which results in the synthesis of energy-rich APT molecules. Since this phosphorylation is occurring in presence of light, it is called photophosphorylation. Depending upon the path of electrons in the electron-transport-system of the primary photochemical reaction, there are two types of photophosphorylation processes. They are (1) Cyclic photophosphorylation and (2) Noncyclic photophosphorylation. The present post discusses the similarities and differences between cyclic and noncyclic photophosphorylation with a comparison table.