Trace the fate of a molecule of water after it reaches the mesophyll cells.

Explanation

**Step-by-Step Solution:**

1. **Arrival at Mesophyll Cells**: When a molecule of water (H2O) enters the mesophyll cells of a leaf, it is primarily absorbed through the roots and transported via the xylem to the leaves.

2. **Role in Photosynthesis**: In the mesophyll cells, water plays a crucial role in the process of photosynthesis, particularly during the light-dependent reactions.

3. **Light Absorption**: The chlorophyll pigments present in the thylakoid membranes of the chloroplasts absorb light energy. This light energy excites the electrons in the chlorophyll molecules.

...