NEETBotanyPhotosynthesis in Higher Plants
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Stroma lamellae of chloroplasts synthesize ATP but are unable to synthesize NADPH + H ^+ during the light reaction. Reason (R): Stroma lamellae membranes lack both Photosystem II (PS II) and the NADP reductase enzyme. In the light of the above statements, choose the most appropriate answer from the
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Step-by-step solution
The stroma lamellae membranes lack PS II as well as the NADP reductase enzyme. Because of this structural limitation, the excited electron does not pass on to NADP ^+ but is cycled back to the PS I complex through the electron transport chain. This cyclic flow of electrons results only in the synthesis of ATP, but not of NADPH + H ^+ . Therefore, the structural absence of PS II and NADP reductase (Reason) is the exact cause for the inability to synthesize NADPH (Assertion). Thus, both Assertion and Reason are true,