Question

The electron transport chain (ETC), transfers electrons between molecules in a series of oxidation-reduction reactions to generate a difference in pH across the thylakoid membrane. How is the energy, generated through electron transfer, used to establish the pH gradient?

• A. From the formation of molecular oxygen through the acceptance of electrons at the end of ETC.
• B. From water being split in Photosystem I.
• C. By powering the movement of protons into the thylakoid space.
• D. By the transfer of CO${}_2$ into the stroma.

Answer 1

Answer: (C)

By powering the movement of protons into the thylakoid space.

The ETC transfers high energy e${}^{-s}$ from one protein complex to other. During this transfer a large number of free energy is released which is utilized to pump H${}^{+s}$ into thylakoid space. Resulting in a pH and electric gradient across the membrane.

So, the correct answer is 'By powering the movement of protons into the thylakoid space'