Photophosphorylation is the method of using light energy from photosynthesis to convert ADP to ATP. It is the method of synthesizing energy-rich ATP molecules by carrying the phosphate
group into an ADP molecule. ATP is the essential universal energy “currency” for any known life form. Photosynthesis requires Photolysis and a continuous unidirectional flow of electrons from water to Photosystem II.
Light energy gets used and forms a high-energy electron donor and a lower-energy electron acceptor system. Then the electrons move instantaneously from donor to acceptor through an electron transport chain.
Photophosphorylation exists of two kinds:
The photophosphorylation process which results in the movement of the electrons cyclically for synthesizing ATP molecules is called Cyclic Photophosphorylation. It will take place in both aerobic wells as anaerobic conditions.
In this process, plant cells finish the ADP to ATP for instant energy for cells. This process regularly takes place in the thylakoid membrane and uses Photosystem I and the chlorophyll P700.
During Cyclic Photophosphorylation, the electrons are shifted back to P700 rather than moving into the NADP from the electron acceptor. This downward flow of electrons from an acceptor to P700 affects the structure of ATP molecules.
This Photophosphorylation occurs on the stroma lamellae, also called fret channels. When it comes to Cyclic Photophosphorylation, high-energy electrons released from P700 of PS1 flow down on a cyclic path. In cyclic electron flow, an electron starts its journey in a pigment complex called Photosystem-I. It then passes from the first acceptor to ferredoxin and then to plastoquinone. Next it reaches cytochrome b6f and then to plastocyanin before returning Photosystem I.
This chain of transport results in a proton-motive force. It pumps H+ ions across the membrane and produces a concentration gradient used to power ATP synthase during chemiosmosis. This pathway is known as Cyclic Photophosphorylation, and it produces neither O2 nor NADPH. Unlike non-cyclic Photophosphorylation, NADP+ does not accept the electrons; and they are sent back to the cytochrome b6f complex.
In bacterial photosynthesis, a single photosystem is involved in Cyclic Photophosphorylation. It is considered favorable in anaerobic conditions and conditions of CO2 compensation points and of high irradiance.
The moving of electrons in a Non-cyclic manner to produce ATP molecules using the energy from excited electrons provided by Photosystem II is known as Non-cyclic Photophosphorylation.
The difference is: