The light-dependent reactions of photosynthesis include splitting of water in presence of sunlight followed by transfer of released electrons from PSII to PSI via intermediate carriers. The electrons finally reduce the NADP+ into NADPH.
As the electrons move from carriers between PSII and PSI, the protons are pumped into thylakoid lumen and an electrochemical gradient is generated. movement of protons back to the stroma via proton channel drives ATP synthesis.
The NADPH and ATP formed during light reactions are channeled into the Calvin cycle. Here, NADPH serves in redox reactions while ATP serves as an energy source to fix the atmospheric CO2 into glucose.
