Multiple Choice
During the light reactions, photosystem I functions to_________, and photosystem II functions to __________.
a) Reduce CO2; oxidize NADPH.
b) Synthesize ATP; Produce O2.
c) Produce O2; oxidize NADPH.
d) Reduce NADP+; oxidize H2O.
9. Photosynthesis
Light Reactions of Photosynthesis
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Which of the following is cycled in the cyclic variation of the light reactions?
A
ATP
B
NADPH
C
Ribulose bisphosphate
D
Protons
E
Electrons
Verified step by step guidance1
Understand the context: The light reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and involve the conversion of light energy into chemical energy.
Identify the cyclic electron flow: In the cyclic variation of the light reactions, electrons are cycled back to the photosystem rather than being used to reduce NADP+ to NADPH.
Recognize the role of electrons: Electrons are excited by light energy and transferred through a series of proteins in the electron transport chain, eventually returning to the photosystem in cyclic electron flow.
Differentiate between cyclic and non-cyclic flow: In non-cyclic electron flow, electrons are used to produce both ATP and NADPH, while in cyclic flow, only ATP is produced, and electrons return to the photosystem.
Conclude that electrons are the component cycled in the cyclic variation of the light reactions, as they are repeatedly excited and returned to the photosystem.
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