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Photosynthesis usually refers to oxygenic photosynthesis, a process that produces oxygen. Photosynthetic organisms store the chemical energy so produced within intracellular organic compounds (compounds containing carbon) like sugars, glycogen , cellulose and starches .
Photoautotrophs are organisms that can utilize light energy from sunlight and elements (such as carbon) from inorganic compounds to produce organic materials needed to sustain their own metabolism (i.e. autotrophy). Such biological activities are known as photosynthesis, and examples of such organisms include plants, algae and cyanobacteria.
In cyclic photophosphorylation, the high-energy electron released from P700, a pigment in a complex called photosystem I, flows in a cyclic pathway. The electron starts in photosystem I, passes from the primary electron acceptor to ferredoxin and then to plastoquinone , next to cytochrome b 6 f (a similar complex to that found in mitochondria ...
Electrons in pigment molecules can exist at specific energy levels. Under normal circumstances, they are at the lowest possible energy level, the ground state. However, absorption of light of the right photon energy can lift them to a higher energy level. Any light that has too little or too much energy cannot be absorbed and is reflected.
The antenna complex contains hundreds of chlorophyll molecules which funnel the excitation energy to the center of the photosystem. At the reaction center, the energy will be trapped and transferred to produce a high energy molecule. [2] The main function of PSII is to efficiently split water into oxygen molecules and protons.
Reaction centers are present in all green plants, algae, and many bacteria.A variety in light-harvesting complexes exist across the photosynthetic species. Green plants and algae have two different types of reaction centers that are part of larger supercomplexes known as P700 in Photosystem I and P680 in Photosystem II.
In 2011 the OEC of PSII was resolved to a level of 1.9Å revealing five oxygen atoms serving as oxo bridges linking the five metal atoms and four water molecules bound to the Mn 4 CaO 5 cluster; more than 1,300 water molecules were found in each photosystem II monomer, some forming extensive hydrogen-bonding networks that may serve as channels ...
4) was discovered in 2001, [45] [46] and was assumed to exist in one of the six phases of solid oxygen. It was proven in 2006 that this phase, created by pressurizing O 2 to 20 GPa, is in fact a rhombohedral O 8 cluster. [47] This cluster has the potential to be a much more powerful oxidizer than either O 2 or O 3 and may therefore be used in ...