Question

NADP+ is reduced to NADPH in

• A. PS 1
• B. PS II
• C. Calvin cycle
• D. noncyclic photophosphorylation.

Answer 1

The Correct Option is D

The question asks about the process where NADP⁺ is reduced to NADPH. This occurs during the photosynthesis process in plants. Let's go through the options to determine the correct answer.

1. PS I (Photosystem I): This is part of the light-dependent reactions of photosynthesis. It helps in the formation of NADPH by providing the electrons necessary to reduce NADP⁺ to NADPH after electron excitation. However, it is not the complete process where noncyclic photophosphorylation occurs on its own.
2. PS II (Photosystem II): This initiates the light-dependent reactions by absorbing light and splitting water molecules, but it primarily contributes electrons that flow through the chloroplast's electron transport chain to ultimately run PS I.
3. Calvin Cycle: This cycle is a part of the light-independent reactions that utilize NADPH and ATP to convert CO₂ into glucose. NADPH is consumed here, not produced.
4. Noncyclic Photophosphorylation: This is the correct answer. It refers to the light-dependent reactions that involve both Photosystem II and Photosystem I, where water molecules are split (photolysis), and oxygen is released as a byproduct. Electrons from water are transferred sequentially through Photosystems II and I and contribute to reducing NADP⁺ to NADPH. This process produces ATP and NADPH, which are used in the Calvin Cycle.

Hence, the correct answer is noncyclic photophosphorylation, where NADP⁺ is reduced to NADPH.