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Multiple Choice
Which of the following best describes the primary function of the light-dependent reactions in photosynthesis?
A
To break down glucose into pyruvate
B
To fix carbon dioxide into glucose
C
To convert solar energy into chemical energy in the form of ATP and NADPH
D
To produce oxygen by splitting carbon dioxide
Verified step by step guidance
1
Understand the context: Photosynthesis occurs in two main stages - the light-dependent reactions and the Calvin cycle (light-independent reactions). The light-dependent reactions take place in the thylakoid membranes of the chloroplasts.
Identify the purpose of the light-dependent reactions: These reactions capture solar energy and convert it into chemical energy in the form of ATP and NADPH, which are then used in the Calvin cycle to synthesize glucose.
Clarify the process: During the light-dependent reactions, chlorophyll absorbs sunlight, exciting electrons. These high-energy electrons are passed through the electron transport chain, leading to the production of ATP via photophosphorylation and the reduction of NADP⁺ to NADPH.
Address oxygen production: Water molecules are split (photolysis) during the light-dependent reactions to replace the excited electrons in chlorophyll. This process releases oxygen as a byproduct, but oxygen production is not the primary function of these reactions.
Eliminate incorrect options: Breaking down glucose into pyruvate occurs in cellular respiration, not photosynthesis. Fixing carbon dioxide into glucose happens in the Calvin cycle, not the light-dependent reactions. The correct answer is that the light-dependent reactions convert solar energy into chemical energy in the form of ATP and NADPH.