Final answer:
H2O (water) serves as a source of hydrogen atoms in the light-dependent reactions of photosynthesis, which generate ATP and NADPH.
Step-by-step explanation:
The role of H2O (water) during photosynthesis is to serve as a source of hydrogen atoms in the light-dependent reactions. These reactions occur in the thylakoid membrane of the chloroplasts, and they require water as a substrate. Water molecules are split during a process known as photolysis, releasing oxygen, protons (H+), and electrons. The oxygen is released into the atmosphere, while the protons and electrons are used to generate ATP and reduce NADP+ to NADPH, which are energy-rich molecules used in the light-independent reactions.
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