fotosynteesiin

Fotosynteesiin, known in English as photosynthesis, is a biological process that occurs primarily in plants, algae, and certain bacteria. It involves the conversion of light energy, usually from the sun, into chemical energy stored in bonds of glucose molecules. This process is fundamental to life on Earth, as it provides the primary energy source for all heterotrophic organisms and contributes to the oxygen content of the atmosphere.

The process takes place mostly in the chloroplasts of plant cells, which contain the pigment chlorophyll. Chlorophyll absorbs light most efficiently in the blue and red wavelengths, harnessing this energy to drive the reactions. Photosynthesis can be summarized in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).

In the light-dependent reactions, light energy excites electrons within chlorophyll molecules, leading to the generation of ATP and NADPH, energy carriers used in later stages. Simultaneously, water molecules are split (photolysis), releasing oxygen as a byproduct.

The Calvin cycle, or light-independent reactions, uses ATP and NADPH to convert carbon dioxide (CO₂) into glucose through a series of enzymatic steps. This process fixes atmospheric carbon into organic molecules, forming the basis of the food chain.

Photosynthesis not only sustains plant life but also maintains atmospheric oxygen levels and influences global carbon cycles. Its efficiency can be affected by environmental factors like light intensity, temperature, and CO₂ concentration. Understanding photosynthesis is crucial for studies related to ecology, agriculture, and climate change mitigation.