Energy efficiency of photosynthesis - Encyclopedia …
What Is Photosynthesis? From Light Energy to Chemical Energy
Photosystem II (PSII) initiates photosynthesis in plants through the absorption of light and subsequent conversion of excitation energy to chemical energy via charge separation. The pigment binding proteins associated with PSII assemble in the grana membrane into PSII supercomplexes and surrounding light harvesting complex II trimers. To understand the high efficiency of light harvesting in PSII requires quantitative insight into energy transfer and charge separation in PSII supercomplexes. We have constructed the first structure-based model of energy transfer in PSII supercomplexes. This model shows that the kinetics of light harvesting cannot be simplified to a single rate limiting step. Instead, substantial contributions arise from both excitation diffusion through the antenna pigments and transfer from the antenna to the reaction center (RC), where charge separation occurs. Because of the lack of a rate-limiting step, fitting kinetic models to fluorescence lifetime data cannot be used to derive mechanistic insight on light harvesting in PSII. This model will clarify the interpretation of chlorophyll fluorescence data from PSII supercomplexes, grana membranes, and leaves.
The maximum efficiency of photosynthesis (PDF …
Nuclear fusion can result in the merging of two nuclei to form a larger one, along with the release of significantly more energy per atom than any chemical process. It occurs only under conditions of extremely high temperature and pressure. Nuclear fusion taking place in the cores of stars provides the energy released (as light) from those stars and produced all of the more massive atoms from primordial hydrogen. Thus the elements found on Earth and throughout the universe (other than hydrogen and most of helium, which are primordial) were formed in the stars or supernovas by fusion processes.
The Future of Fuel Cells - Ben Wiens Energy Science Site
We'll look at a simpler example of photosynthesis first, and use it as an introduction to photosynthesis in plants and cyanobacteria (blue-green algae). Although the primary reactions of photosynthesis take place at "photosynthetic reaction centers," the first level of interaction of light with an organism that carries out photosynthesis is at an assembly of chlorophyll molecules that "harvest" light (the "light-harvesting complex"). Such an assembly results in a greater chance that photons will be captured and, because of the strategic arrangement of the individual chlorophyll and other accessory light-absorbing molecules, the transfer of energy to the photosynthetic reaction center is very fast (-10 s) and very efficient (>90%).