Question

What is the role of the electron transport chain in the light dependent reactions of
photosynthesis?

Answer 1

Electron transport chain plays an important role in generation of ATP and NADPH. In phoyosynthesis the light dependent reaction takes place in stroma of thalakoid which contain integral membrane protein complexes: Photosystem II, Cytochrome b6f complex, Photosystem I and ATP synthase. These complexes work in coordination to produce ATP and NADPH. In the first part of light dependent reaction, chlorophyll a pigment of photosystem II absorbs photons from sunlight expelling an electron. The transfer of electron from one molecule to another creats a chain of redox reactions i. e electron transport chain. The electron flows from photosystem II to ctychrome b6f to photosystem I. Cytochrome b6f and ATP synthase work together to create ATP. An electrochemical gradient is generated when energy travels through electron transport chain pumping hydrogen ions into thylakoid space. The protons flow through ATP synthase from the thylakoid space into stroma by chemiosmosis to form ATP molecules. These ATP molecules are then used for the formation of sugar molecules in the second stage of photosynthesis. In the second part of light dependent reaction, photosystem I absorbs second photon and the electron gets expelled. This results in the formation of NADPH molecule. Both ATP and NADPH is used in the light independent reaction to synthesize glucose.