Photosynthese

Photosynthese, commonly called photosynthesis, is the biological process by which light energy is converted into chemical energy in photoautotrophic organisms such as plants, algae, and cyanobacteria. It enables the synthesis of organic compounds from carbon dioxide and water, releasing oxygen as a byproduct and supporting most life on Earth.

The process typically involves two stages. In the light-dependent reactions, performed in the thylakoid membranes, chlorophyll and other pigments absorb light to drive water splitting, releasing O2 and transferring electrons through the photosynthetic electron transport chain to generate ATP and NADPH. In the Calvin cycle, or light-independent reactions, located in the stroma, ATP and NADPH power carbon fixation: CO2 is incorporated into sugars byRuBisCO and ultimately converted to glyceraldehyde-3-phosphate, which can form glucose and other carbohydrates.

Pigments such as chlorophylls A and B and carotenoids capture light across a range of wavelengths, broadening energy capture. The overall stoichiometric equation is 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2.

Some plants use C3, C4, or CAM pathways to optimize photosynthesis under different temperatures and water conditions. Photosynthesis underpins the global carbon cycle, fuels plant growth, and supports agriculture. It is the focus of ongoing research into crop improvement and artificial photosynthesis, aiming to harness light energy more efficiently.