In the light reactions, what happens to water molecules?

In the light reactions of photosynthesis, water molecules undergo a process known as photolysis, where they are split into oxygen, hydrogen ions (protons), and electrons under the influence of light energy. This process takes place in the thylakoid membranes of the chloroplasts. The oxygen produced during this reaction is released into the atmosphere as a byproduct.

Additionally, the electrons released from the splitting of water are essential for the electron transport chain that occurs in the light reactions, while the hydrogen ions contribute to the proton gradient used to generate ATP and reduce NADP+ to NADPH. This makes the splitting of water a crucial step in the conversion of light energy into chemical energy during photosynthesis.

Other options relate to basic functions and components of photosynthesis but do not accurately describe what occurs to water molecules during the light reactions. Glucose formation is a process that takes place later in the Calvin cycle, not directly associated with the light reactions. Chlorophyll does capture light energy but does not absorb water, and while thylakoids are involved in the reactions, they do not store water but rather facilitate the light-dependent reactions where water is utilized.