LightHarvesting

Lightharvesting, often referred to as light harvesting, is the biological process by which photosynthetic organisms capture sunlight and funnel its energy toward reaction centers where it is converted into chemical energy. In plants, algae, and cyanobacteria, light is absorbed by pigment–protein complexes that act as antennae. The main pigments are chlorophylls and carotenoids; in cyanobacteria there are phycobiliproteins arranged in phycobilisomes. These pigments form antenna complexes that capture photons and transfer excitation energy via resonant energy transfer to the core reaction centers of photosystems I and II.

Energy transfer proceeds as excitons hop between pigments until they reach the reaction center, where a pigment molecule donates an electron to an electron acceptor, initiating a photosynthetic charge separation and the subsequent electron transport chain that drives ATP and NADPH formation. The efficiency of energy transfer depends on pigment arrangement, spectral overlap, and the local environment within the thylakoid membrane. The system also includes protective mechanisms to prevent damage when light is excessive, such as non-photochemical quenching, which dissipates surplus energy as heat.

Organisms regulate light harvesting to balance energy capture with photoprotection. Plants can perform state transitions to optimize energy distribution between photosystems, while non-photochemical quenching responds to rapid changes in light intensity. Adaptations vary among organisms: higher plants rely heavily on LHCII antennas, while cyanobacteria employ phycobilisomes with different spectral properties.

In research and technology, principles of natural lightharvesting inform attempts to develop artificial or hybrid solar-energy systems. Efforts include designing synthetic antenna arrays and studying energy transfer mechanisms for improved light capture and conversion, with ongoing work to integrate these systems with efficient charge separation and stability requirements.