Search results
Results from the WOW.Com Content Network
Triplet chlorophyll is a potent photosensitiser of molecular oxygen forming singlet oxygen which can cause oxidative damage to the pigments, lipids and proteins of the photosynthetic thylakoid membrane. To counter this problem, one photoprotective mechanism is so-called non-photochemical quenching (NPQ), which relies upon the conversion and ...
The excited, triplet state photosensitizer then reacts with a substrate molecule which is not molecular oxygen to both form a product and reform the photosensitizer. Type I photosensitized reactions result in the photosensitizer being quenched by a different chemical substrate than molecular oxygen.
Light-harvesting complexes are found in a wide variety among the different photosynthetic species, with no homology among the major groups. [4] The complexes consist of proteins and photosynthetic pigments and surround a photosynthetic reaction center to focus energy, attained from photons absorbed by the pigment , toward the reaction center ...
As in cyanobacteria and chloroplasts, this is a solid-state process that depends on the precise orientation of various functional groups within a complex transmembrane macromolecular structure. To make NADPH, purple bacteria use an external electron donor (hydrogen, hydrogen sulfide , sulfur, sulfite, or organic molecules such as succinate and ...
The light-harvesting complex (or antenna complex; LH or LHC) is an array of protein and chlorophyll molecules embedded in the thylakoid membrane of plants and cyanobacteria, which transfer light energy to one chlorophyll a molecule at the reaction center of a photosystem. The antenna pigments are predominantly chlorophyll b, xanthophylls, and ...
In these complexes, chlorophyll serves three functions: The function of the vast majority of chlorophyll (up to several hundred molecules per photosystem) is to absorb light. Having done so, these same centers execute their second function: The transfer of that energy by resonance energy transfer to a specific chlorophyll pair in the reaction ...
The long-lived triplet excited state accessible by photoexcitation is both a more potent reducing agent and a more potent oxidizing agent than the ground state of the catalyst. Since sensitizer is coordinatively saturated, electron transfer must occur by an outer sphere process, where the electron tunnels between the catalyst and the substrate.
The reaction center is made of two chlorophyll molecules and is therefore referred to as a dimer. [11] The dimer is thought to be composed of one chlorophyll a molecule and one chlorophyll a′ molecule. However, if P700 forms a complex with other antenna molecules, it can no longer be a dimer. [13]