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Multiple Choice
In the process of photosynthesis, how is NADPH formed during Photosystem I (PSI)?
A
By the oxidation of NADPH to NADP+
B
By the direct transfer of electrons from chlorophyll
C
By the reduction of NADP+ using electrons from water
D
By the reduction of NADP+ using electrons from ferredoxin
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.
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.
The excited electrons are passed to a protein called ferredoxin, which acts as an electron carrier. Ferredoxin receives electrons from PSI and becomes reduced.
The reduced ferredoxin then transfers electrons to NADP+ reductase, an enzyme that facilitates the reduction of NADP+ to NADPH.
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.