Photosynthesis

See also: Key enzyme: RuBisCO  –  Limitations on Photosynthesis

Overview

Photosynthesis is the process whereby plants and algae use light energy to fix carbon dioxide as sugars. Although it is often represented by one highly simplified equation – 6H₂O + 6CO₂ –> C₆H₁₂O₆ + 6O₂– it is in reality a more complex series of spatially and temporally separated reactions.

The structure of ATP

Photosynthesis largely comprises two linked processes:

• the light-dependent reactions – in which light energy excites electrons split from water, driving an electron transport chain and proton-pumping which ultimately result in the production of ATP (adenosine triphosphate, the universal biological energy currency) and NADPH (reduced nicotinamide adenine dinucleotide phosphate, a reducing agent)
• the light-independent reactions – the Calvin Cycle, in which CO₂ is fixed into organic molecules by the enzyme RuBisCO.