Question

Assertion: The proton gradient is broken down due to the movement of protons across the membrane to stroma through the transmembrane channel of the $F_0$ of the $ATP$ase.
Reason : The breakdown of proton gradient leads to release of energy.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

Electron transport in photosynthesis produces a proton gradient. The gradient develops inside the thylakoid lumen in chloroplasts. Proton pump is energised by electron flow. It creates a proton gradient or high concentration of $H^{+}$ in the lumen. The proton gradient is broken down due to movement of protons through transmembrane channels, $F_0$ of $ATP$ase. The break down of the gradient provides enough energy to cause a conformational change in the $F_1$ particle of the $ATP$ase, which makes the enzyme synthesise several molecules of energy-packed $ATP$.