Photosynthesis

Photosynthesis, process by which green plants convert the energy of sunlight into chemical energy that is stored as carbohydrate. The process can be written as: 6CO₂+6H₂O→ C₆H₁₂O6+6O₂ (→ = light)

In the “light reaction,” chlorophyll (the key chemical in the whole process) is activated by absorbing a quantum of light, initiating a sequence of reactions in which the energy-rich compounds (ATP) adenosine triphosphate and the reduced form of triphosphopyriden nucleotide (TPNH) are made, water being decomposed to give free oxygen in the process. In the second stage, the “dark reaction,” the ATP and TPNH provide the energy for the assimilation of carbon dioxide gas, yielding a variety of sugars from which other sugars and carbohydrates, including starch, can be built up.