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The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle [1] of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into glucose. The Calvin cycle is present in all photosynthetic eukaryotes and also many ...
The light-harvesting system of PSI uses multiple copies of the same transmembrane proteins used by PSII. The energy of absorbed light (in the form of delocalized, high-energy electrons) is funneled into the reaction center, where it excites special chlorophyll molecules (P700, with maximum light absorption at 700 nm) to a higher energy level.
The light excites an electron in the pigment P680 at the core of photosystem II, which is transferred to the primary electron acceptor, pheophytin, leaving behind P680 +. The energy of P680 + is used in two steps to split a water molecule into 2H + + 1/2 O 2 + 2e-(photolysis or light-splitting).
Photosynthesis (/ ˌ f oʊ t ə ˈ s ɪ n θ ə s ɪ s / FOH-tə-SINTH-ə-sis) [1] is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabolism.
Photons trapped by photosystem II move the system from state S 0 to S 1 to S 2 to S 3 and finally to S 4. S 4 reacts with water producing free oxygen: 2 H 2 O → O 2 + 4 H + + 4 e −. This conversion resets the catalyst to the S 0 state. The active site of the OEC consists of a cluster of manganese and calcium with the formula Mn 4 Ca 1 O x ...
This energy state is unstable, therefore it will return to the ground state by lowering its energy. It can do that in more than one way: it can react further, without any light emission; it can lose energy without emission, for example, giving off heat to the surroundings or transferring energy to another molecule; it can emit light
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Photobiology is the scientific study of the beneficial and harmful interactions of light (technically, non-ionizing radiation) in living organisms. [1] The field includes the study of photophysics, photochemistry, photosynthesis, photomorphogenesis, visual processing, circadian rhythms, photomovement, bioluminescence, and ultraviolet radiation effects.