fotosyntez

Fotosyntez is the process by which light energy is converted into chemical energy, enabling plants, algae, and some bacteria to synthesize organic compounds from carbon dioxide and water. Oxygenic photosynthesis, the most common form, releases molecular oxygen as a byproduct.

In oxygenic photosynthesis, energy from light drives two linked stages: the light-dependent reactions and the Calvin cycle. The light reactions occur in the thylakoid membranes of chloroplasts, where chlorophyll and other pigments absorb light to drive electron transport. Water is split (photolysis), releasing electrons, protons, and O2. The electron transport chain generates ATP and the carrier NADPH.

The Calvin cycle, or C3 pathway, occurs in the stroma and fixes CO2 into organic molecules using ATP and NADPH to produce glyceraldehyde-3-phosphate, a precursor to glucose and other carbohydrates. The enzyme RuBisCO catalyzes the first CO2 fixation step.

Many plants use adaptation variants such as C4 photosynthesis, which concentrates CO2 to increase efficiency in hot conditions, and CAM photosynthesis, which separates CO2 uptake and fixation temporally to reduce water loss.

Fotosyntez is fundamental to life on Earth as the primary source of organic matter for nearly all organisms and the major source of atmospheric O2. It also influences global carbon cycles and energy flow in ecosystems.