Answer :
Final answer:
During the light-dependent reactions of photosynthesis, water molecules are split, releasing oxygen and producing energy carriers like ATP and NADPH. This process occurs in the thylakoid membranes of chloroplasts upon the absorption of sunlight. The other options listed are related to the Calvin cycle, which occurs after the light-dependent reactions.
Explanation:
Light-Dependent Reactions of Photosynthesis
The light-dependent reactions are the initial stage of photosynthesis that occur in the thylakoid membranes of chloroplasts. One of the primary events during these reactions is the splitting of water molecules, a process known as photolysis. This reaction occurs when sunlight is absorbed by chlorophyll, leading to the release of oxygen as a byproduct and the production of energy-rich molecules like ATP and NADPH.
In contrast, the other options listed in the question are associated with the light-independent reactions (Calvin cycle). For example, carbon fixation refers to the incorporation of CO2 into organic molecules during the Calvin cycle, while the reduction of PGA (3-phosphoglycerate) and the regeneration of RuBP (ribulose bisphosphate) are also processes that occur later, during the Calvin cycle. Therefore, the selection that accurately describes a process occurring in the light-dependent reactions of photosynthesis is the splitting of water molecules.
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