Question

Assertion : In case of cyclic photophosphorylation, there is no production of NADPH and oxygen.

Reason : As the electron flows cyclically and NADPH is present in sufficient amount in the cell, hence, cyclic photophosphorylation occurs to provide ATP to power other activities in chloroplast.

• A. Both assertion and reason are true and the reason is a correct explanation of the assertion
  
• B. Both assertion and reason are true but reason is not the correct explanation of the assertion
• C. Assertion is true but the reason is false
  
• D. Both assertion and reason are false

Answer 1

The correct option is A Both assertion and reason are true and the reason is a correct explanation of the assertion


Photosynthsis has two phases: light reaction and dark reaction. Light reaction can be of two types: non-cyclic photophosphorylation and cyclic photo-phosphorylation.

In case of non-cyclic photophosphorylation, ATP and NADPH are produced at the end of the reaction.

In case of cyclic photophosphorylation, the electron that is released from $P_{700}$ comes back to it. Hence, oxygen is not produced as splitting of water molecule is not needed to give electrons to the electron-deficient $P_{700}$ molecule.

Also, as electrons are moving in a cycle, there isn't any terminal electron acceptor and hence, NADPH is not formed. But due to movement of high energy electrons, ATP is produced in cyclic photophosphorylation.

This process occurs when the concentration of NADPH is sufficient in the cell but ATP is not present in sufficient amount. By this process, the cell only produces ATP.