Question

Protons accumulate inside the lumen of thylakoids due to

• A. splitting of water
• B. formation of NADPH
• C. both a and b
• D. formation of ATP

Answer 1

The correct option is A splitting of water

Protons accumulate inside the lumen of thylakoids due to splitting of water. Water splitting complex is associated with PS-II and is located on the inner side of the thylakoid membrane (facing the lumen of thylakoids). It helps in splitting the water. The splitting of water (photolysis of water) results in the release of protons, electrons and oxygen. In the stroma of chloroplast, protons are utilised and NADPH is formed from NADP+. As the lumen of thylakoids has a high concentration of protons and stroma has low concentration of protons, a proton gradient is created. This proton gradient helps in the synthesis of ATP.