Question

Assertion: Cyclic photophosphorylation synthesises ATP.

Reason: ATP synthesis in cyclic photophosphorylation is associated with NADPH formation.

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

The correct option is: (c)

Explanation:

In case of cyclic photophosphorylation, the electron while passing between ferredoxin and plastoquinone and/or over the cytochrome complex, loses sufficient energy to form ATP from ADP and inorganic phosphate. 

In cyclic photophosphorylation no NADPH formation takes place. But in case of non-cyclic photophosphorylation, NADP - reduced through H⁺ released during photolysis forms NADPH. ATP synthesis is not direct and the energy released by electron is actually used for pumping H⁺ ions across the thylakoid membrane. It creates a proton gradient. The gradient triggers the coupling factor to synthesise ATP from ADP and inorganic phosphate.