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Photosynthesis is the process used by plants, algae, and cyanobacteria to convert light energy into chemical energy, through a process that uses sunlight, water, and carbon dioxide. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water. Oxygen is released as a byproduct of photosynthesis.

The overall chemical equation for photosynthesis is: 6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2. This equation represents the net transformation, and the process itself is much more complex, involving a series of biochemical reactions. Photosynthesis occurs primarily in the chloroplasts of plant cells, which contain chlorophyll, the pigment that absorbs light energy.

There are two main stages of photosynthesis: the light-dependent reactions and the light-independent reactions (also known as the Calvin cycle). The light-dependent reactions take place in the thylakoid membranes of chloroplasts and involve the absorption of light energy by chlorophyll. This energy is used to split water molecules, releasing oxygen, and to produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which are energy-carrying molecules.

The light-independent reactions occur in the stroma of the chloroplasts and do not directly require light. In this stage, the ATP and NADPH produced during the light-dependent reactions are used to fix carbon dioxide from the atmosphere and convert it into glucose. This glucose can then be used by the plant for energy, growth, or stored for later use. Photosynthesis is a fundamental process for life on Earth, providing the primary source of energy for most ecosystems and producing the oxygen that most organisms need to breathe.