Photosynthesis is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their activities. Photosynthetic organisms use intracellular organic compounds to store the chemical energy they produce in photosynthesis within organic compounds like sugars, glycogen, cellulose and starches. Photosynthesis is usually used to refer to oxygenic photosynthesis, a process that produces oxygen. To use this stored chemical energy, the organisms' cells metabolize the organic compounds through another process called cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth.
Composite image showing the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation. Dark red and blue-green indicate regions of high photosynthetic activity in the ocean and on land, respectively.
Plant cells with visible chloroplasts (from a moss, Plagiomnium affine)
Portrait of Jan Baptist van Helmont by Mary Beale, c. 1674
Melvin Calvin works in his photosynthesis laboratory.
Photoautotrophs are organisms that can utilize light energy from sunlight and elements from inorganic compounds to produce organic materials needed to sustain their own metabolism. This biological activity is known as photosynthesis, and examples of such photosynthetic organisms include plants, algae and cyanobacteria.
Winogradsky column showing Photoautotrophs in purple and green
