In the process of photosynthesis, how is ${\mathrm{NADPH}}_{}$ formed during Photosystem I (PSI)?

• A. By the oxidation of ${\mathrm{NADPH}}_{}$ to ${\mathrm{NADP}}_{+}$
• B. By the direct transfer of electrons from chlorophyll
• C. By the reduction of ${\mathrm{NADP}}_{+}$ using electrons from water
• D. By the reduction of ${\mathrm{NADP}}_{+}$ using electrons from ferredoxin

Answer: (D)

Verified step by step guidance

1. Photosystem I (PSI) is a crucial component of the photosynthesis process, primarily involved in the light-dependent reactions. It functions to convert light energy into chemical energy.
2. In PSI, light energy is absorbed by chlorophyll molecules, exciting electrons to a higher energy state. These high-energy electrons are then transferred through a series of proteins embedded in the thylakoid membrane.
3. The excited electrons are passed to a protein called ferredoxin, which acts as an electron carrier. Ferredoxin receives electrons from PSI and becomes reduced.
4. The reduced ferredoxin then transfers electrons to NADP+ reductase, an enzyme that facilitates the reduction of NADP+ to NADPH.
5. NADP+ accepts the electrons from ferredoxin and, along with a proton (H+), is reduced to form NADPH. This NADPH is then used in the Calvin cycle to help synthesize glucose from carbon dioxide.