Question

Synthesis of $ADP + Pi \rightarrow ATP$ in grana or photosynthesis is
(a) Phosphorylation
(b) Photophosphorylation
(c) Oxidative phosphorylation
(d) Photolysis

Answer 1

Hint: In the year 1950 for the first time an experiment was conducted to evidence the existence of this process. This was conducted by Otto Kandler with the use of intact Chlorella cells.

Complete answer:
During the process of photosynthesis phosphorylation of ADP occurs to form ATP by the use of light energy from the sun, the entire process is called photophosphorylation. This occurs in both aerobic and anaerobic conditions. Light energy is used to create a high energy electron donor and a lower-energy electron acceptor during photophosphorylation. Then through an electron transport chain, the electron moves from the donor to the acceptor. This transport chain creates a proton-motive force, which is pumping H+ ions across the membrane. As a result, a concentration gradient is produced which is used to power the enzyme ATP synthase. This pathway is also called cyclic photophosphorylation and it produces neither oxygen nor NADPH molecules. The electron transport chain is a series of electron carriers over which electrons pass in a downhill journey releasing energy at every step that is used in generating an electrochemical proton gradient which helps in synthesizing ATP. Based on the path of electrons, the associated photophosphorylation can be identified as non-cyclic and cyclic phosphorylation.
So, the correct answer is,’Photophosphorylation’.

Note: -The photophosphorylation process occurs in the grana of chloroplast during photosynthesis
-The flow of electrons through the electron transport system is linked to photophosphorylation.
-During the process of formation of ATP from ADP and inorganic phosphate (IP) utilizing light energy.
-When the chloroplast runs low on ATP for conducting the Calvin cycle, NADPH will accumulate and the plant may shift from non cyclic to cyclic electron flow.