Question

Energy required for ATP synthesis in PSII comes from

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

Answer 1

The correct option is A Proton gradient

Proton gradient :

• NADP reductase is present in the thylakoid membrane of the chloroplast. It pumps protons in the thylakoid lumen.
• It creates the proton gradient across the thylakoid membrane.
• Protons pass through the ATP synthase enzyme present in the thylakoid membrane and cause the release of ATP into the stroma.
• Thus, the proton gradient helps in the ATP synthesis in PSII.

Electron gradient :

Electron gradient in light reaction in PSI and PSII transfers electrons and helps in the synthesis of NADPH and not ATP.

Reduction of glucose :

The reduction of glucose that occurs during a dark reaction requires the breakdown of ATP rather than the synthesis of ATP. Thus, the reduction of glucose does not lead to the synthesis of ATP.

Oxidation of glucose :

Oxidation of glucose occurs in glycolysis in the cytoplasm and eventually results in ATP synthesis but this ATP synthesis is not involved in the PSII.

Final answer :

Proton gradient.