Light striking chlorophyll molecules causes them to lose electrons, which are ultimately replaced by electrons obtained from water molecules.

Here's a breakdown of the process:

1. Light Absorption: Chlorophyll absorbs light energy, causing an electron to jump to a higher energy level.

2. Electron Transfer: This excited electron is then passed along an electron transport chain, a series of molecules embedded in the thylakoid membrane of chloroplasts.

3. Water Splitting: To replenish the electrons lost by chlorophyll, water molecules are split into hydrogen ions (H+), electrons, and oxygen. The electrons from water replace those lost by chlorophyll.

4. ATP and NADPH Production: The energy from the electron transport chain is used to generate ATP (adenosine triphosphate), the energy currency of the cell, and NADPH, a reducing agent.

This entire process is known as photosynthesis, and it's how plants convert light energy into chemical energy in the form of sugars.