fotosyntheze

Fotosyntheze is the process by which certain organisms convert light energy into chemical energy, typically forming carbohydrates from carbon dioxide and water. The term is a variant spelling of photosynthesis and is used primarily in informal contexts or in translations of the word from other languages. It is central to the energy flow in most ecosystems, providing the foundational food source for heterotrophic organisms.

The process occurs in specialized organelles called chloroplasts in plants and algae, and in thylakoid membranes of cyanobacteria. Light energy is absorbed by pigments, most notably chlorophyll, which excites electrons to a higher energy level. These high-energy electrons travel through a series of protein complexes in the electron transport chain, generating a proton gradient that drives the synthesis of adenosine triphosphate (ATP) and the reducing power in the form of NADPH. CO₂ is then fixed into organic molecules in the Calvin cycle, producing sugars that can be used immediately or stored as starch.

Fotosyntheze is divided into two major phases. The light-dependent reactions rely directly on photon absorption and yield ATP and NADPH while producing oxygen as a by-product. The light-independent or Calvin cycle uses ATP and NADPH to reduce CO₂, producing ribulose‑1,5‑bisphosphate as a substrate for successive cycles that generate glucose.

Beyond its ecological importance, fotosyntheze supports the earth’s oxygen levels, contributes to carbon sequestration, and offers insights for bioengineering and renewable energy research. The study of this process has led to advances in artificial photosynthesis efforts, aiming to mimic natural catalysis for sustainable fuel production. Despite its simplicity, fotosyntheze remains a diverse field of research encompassing biochemistry, molecular biology, and environmental science.