Question

ADP $⟶$ ATP reaction occurs when two protons ($H^{+}$) are passed from

• A. Thylakoid to cytosol
• B. Thylakoid to lumen
• C. Lumen of thylakoid to stroma
• D. Stroma to thylakoid lumen.

Answer 1

The correct option is C Lumen of thylakoid to stroma

According to the chemiosmotic hypothesis of ATP synthesis, ATP synthase enzyme synthesizes ATP by chemiosmosis. It allows protons to pass through the membrane. In this process, two protons (H${}^{+}$) are released from the thylakoid lumen and are taken up from the stroma. This generates a proton gradient. This free energy difference is used to phosphorylate ADP to make ATP.

Thus, the correct answer is 'Lumen of thylakoid to stroma.'