Question

Which is the role of the electron transport chain in the process of photosynthesis?

A.
cycling electrons between photosystem I and photosystem II
B.
adding energy to the electrons that enter photosystem I
C.
carrying electrons from photosystem II, to photosystem I, to NADP+
D.
removing electrons from the chloroplast

Answer 1

The electron transport chain in photosynthesis transfers high-energy electrons from PSII to PSI and on to NADP+, pumps protons to create an electrochemical gradient, and produces ATP and NADPH for the Calvin cycle.

Step-by-step explanation:

The role of the electron transport chain (ETC) in photosynthesis is to carry electrons from photosystem II (PSII), to photosystem I (PSI), and eventually to NADP+ to form NADPH. This process is part of the light-dependent reactions in photosynthesis, where the ETC plays a critical role in converting light energy into chemical energy in the form of ATP and NADPH. These molecules provide the energy and reducing power necessary for the Calvin cycle, where sugar is produced.

Photosystem II is the initial site where photons of light are absorbed, which results in the excitation of electrons. These high-energy electrons are then passed to the electron transport chain. During their transit, energy is transferred from the electrons to pump protons into the thylakoid lumen, thus creating an electrochemical gradient. Finally, the electrons are transferred to PSI where they are used to reduce NADP+ to NADPH. Simultaneously, the proton gradient drives ATP synthase to produce ATP. The initial source of electrons for the electron transport chain is the oxidation of water at PSII, which also releases oxygen into the atmosphere.