fotosynteesiessä

fotosynteesiessä refers to the process by which photosynthetic organisms, such as plants, algae, and cyanobacteria, convert light energy into chemical energy. In this process, chlorophyll and other pigment molecules located in the thylakoid membranes absorb photons, initiating a cascade of reactions that generate the electron carriers ATP and NADPH. The light-dependent reactions also produce oxygen as a by‑product when water molecules are split through photolysis.

The reducing power generated in the light‑dependent reactions is then used in the light‑independent or Calvin cycle. Carbon dioxide from the atmosphere is fixed into organic molecules, ultimately forming glucose and other carbohydrates. The enzymes ribulose‑1,5‑biphosphate carboxylase/oxygenase (RuBisCO) catalyzes the key carboxylation step that incorporates CO₂ into a five‑carbon sugar.

Energy and reducing equivalents produced under sunlight are stored in energy‑rich bonds of carbohydrates, which serve as a food source for autotrophs and, indirectly, for heterotrophic organisms. The balance between the light reactions and the Calvin cycle is tightly regulated; environmental factors such as light intensity, temperature, and water availability influence the efficiency of photosynthesis.

fotosynteesiessä also plays a critical ecological role by providing the primary source of atmospheric oxygen and forming the base of food webs. Advances in molecular biology and biophysics continue to elucidate the detailed mechanisms of photosynthetic light harvesting, electron transport, and carbon fixation, offering potential applications in bioenergy and climate change mitigation.