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Multiple Choice
Which of the following represents a reactant or input for the light reaction of photosynthesis?
A
Glucose (C6H12O6)
B
Water (H2O)
C
Carbon dioxide (CO2)
D
Oxygen (O2)
Verified step by step guidance
1
Understand the light reactions of photosynthesis: These reactions occur in the thylakoid membranes of chloroplasts and require light energy to produce ATP and NADPH.
Identify the inputs for the light reactions: The primary reactants are water (H2O) and light energy. Water is split in a process called photolysis, releasing oxygen (O2) as a byproduct.
Recognize that glucose (C6H12O6) and carbon dioxide (CO2) are not inputs for the light reactions: Glucose is a product of the Calvin cycle, which occurs after the light reactions, and carbon dioxide is used in the Calvin cycle, not the light reactions.
Note that oxygen (O2) is a product, not a reactant, of the light reactions: It is released when water is split during photolysis.
Conclude that water (H2O) is the correct reactant for the light reactions of photosynthesis, as it provides electrons and protons needed for the production of ATP and NADPH.