Question

Energy required for ATP synthesis in PS II comes from

• A. Proton gradient
• B. Electron gradient
• C. Reduction of glucose
• D. Oxidation of glucose

Answer 1

The correct option is A Proton gradient

2H₂O -------------------------> 4H⁺ + O₂ + 4e⁻

This reaction takes place in the inner side of the thylakoid membrane, and so the protons formed are thus trapped in the lumen of thylakoid.

As electrons move through photosystems, these protons are transported across the membrane.

This gradient is important because the breakdown of this leads to the release of energy.

So, the correct answer is 'Proton gradient'