By Mary Dowd, Updated Aug 30 2022
Photosynthesis is a remarkably efficient chemical reaction that turns sunlight, water, and atmospheric carbon dioxide into glucose, the energy currency of life. Plants extract water from the soil and absorb CO₂ through tiny pores called stomata, combining these inputs to synthesize food and release oxygen as a by‑product.
The balanced chemical equation for the process is:
6 H₂O + 6 CO₂ + sunlight → C₆H₁₂O₆ + 6 O₂
This equation shows that six molecules of water and six molecules of carbon dioxide, when energized by sunlight, produce one molecule of glucose and six molecules of oxygen.
About 3.5 billion years ago, cyanobacteria harnessed light energy to convert inorganic compounds into chemical energy, laying the foundation for life on Earth. According to Quanta Magazine, these ancient microbes set the stage for the evolution of diverse photosynthetic organisms and the oxygenation of our atmosphere.
Photosynthetic organisms form the base of every food web, providing energy for herbivores, omnivores, and higher predators. They also regulate atmospheric gases by producing oxygen and sequestering carbon dioxide—a process known as carbon fixation. Over geological time, the burial of plant material can lead to fossil fuel formation.
Water is essential for transporting nutrients and sugars throughout a plant’s tissues. It fills large vacuoles that maintain turgor pressure, supporting stems and leaves and enabling photosynthetic cells to remain active. When water is scarce, cells lose turgor, stems droop, and photosynthesis slows.
Students can explore the importance of water by growing bean sprouts and manipulating environmental variables. A typical experiment might involve:
Conducting each experiment with at least five plants ensures a robust sample size and reliable data.
