Photosynthesizers

Photosynthesizers are organisms that capture light energy and convert it into chemical energy through photosynthesis. This group includes plants, algae, and cyanobacteria, and also certain bacteria that perform anoxygenic photosynthesis. These organisms form the base of most ecosystems by producing organic matter from carbon dioxide and releasing oxygen.

In oxygenic photosynthesis, light is absorbed by pigment–protein complexes (primarily chlorophyll a and chlorophyll b, with carotenoids as accessory pigments) housed in chloroplasts in plants and algae or in photosynthetic membranes in cyanobacteria. Light-dependent reactions take place in the thylakoid membranes, generating ATP and NADPH and releasing O2 from water. The ATP and NADPH power the Calvin cycle (carbon fixation) in which CO2 is converted into sugars such as glyceraldehyde-3-phosphate.

Most land plants use C3 photosynthesis, some use C4 or CAM pathways as adaptations to water availability and heat, affecting efficiency and distribution.

In addition to oxygenic photosynthesis, anoxygenic photosynthesis is carried out by certain bacteria and does not produce oxygen; these organisms use other electron donors and pigments (e.g., bacteriochlorophyll) and often inhabit anaerobic or light-rich environments.

Photosynthesizers sustain global food webs and drive biogeochemical cycles. They are also a major focus of research for bioenergy, carbon capture, and the development of artificial photosynthesis technologies.