A plant cell uses the light energy it captures in a process called photosynthesis. Here's how it works:

1. Light absorption: Chlorophyll, a green pigment in chloroplasts, absorbs light energy, primarily in the red and blue wavelengths.

2. Water splitting: The light energy is used to split water molecules (H₂O) into hydrogen ions (H+) and oxygen (O₂). The oxygen is released as a byproduct.

3. Energy storage: The energy from light is used to convert carbon dioxide (CO₂) from the air into glucose (C₆H₁₂O₆), a sugar that stores energy. This process is called carbon fixation.

Essentially, a plant cell uses light energy to:

* Make food: Glucose, the sugar produced during photosynthesis, is the plant's primary source of energy for growth and other processes.

* Produce oxygen: The oxygen released during photosynthesis is essential for the survival of most living organisms, including humans.

In summary, plant cells use light energy to convert inorganic substances (water and carbon dioxide) into organic molecules (glucose) and release oxygen as a byproduct. This process of photosynthesis is crucial for the survival of both plants and other living organisms.