NADP reductase enzyme is present on the

stroma side of the thylakoid membrane

The NADP reductase enzyme is located on the stroma side of the thylakoid membrane within chloroplasts. This strategic positioning facilitates its crucial role in photosynthesis.

Explanation:

• Location: The enzyme is situated on the stroma side (the inner side facing the chloroplast stroma) of the thylakoid membrane. This placement is essential for its function in the light-dependent reactions of photosynthesis.
• Function: NADP reductase catalyzes the transfer of electrons from ferredoxin to NADP⁺, resulting in the formation of NADPH. The reaction is as follows:
  • NADP⁺ + H⁺ + 2e⁻ → NADPH
• Role in Photosynthesis: NADPH produced by NADP reductase serves as a reducing agent, providing the necessary electrons and hydrogen ions for the Calvin cycle, where atmospheric CO₂ is fixed into organic molecules.
• Proton Gradient Contribution: The activity of NADP reductase contributes to the proton gradient across the thylakoid membrane. By facilitating the removal of protons (H⁺) from the stroma to form NADPH, it helps maintain the proton motive force essential for ATP synthesis.

Understanding the precise location and function of the NADP reductase enzyme elucidates its vital role in the photosynthetic process, particularly in the production of NADPH and the maintenance of the proton gradient necessary for ATP synthesis.