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NADH dehydrogenase → plastoquinol → b 6 f → cyt c 6 → cyt aa 3 → O 2. where the mobile electron carriers are plastoquinol and cytochrome c 6, while the proton pumps are NADH dehydrogenase, cyt b 6 f and cytochrome aa 3 (member of the COX3 family). Cyanobacteria are the only bacteria that produce oxygen during photosynthesis.
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). An electron from the water molecule reduces P680 + back to P680, while the H + and oxygen are released.
[4] Cyanobacteria is the only prokaryotic group that performs oxygenic photosynthesis. Anoxygenic photosynthetic bacteria use PSI- and PSII-like photosystems, which are pigment protein complexes for capturing light. [5] Both of these photosystems use bacteriochlorophyll. There are multiple hypotheses for how oxygenic photosynthesis evolved.
Calvin cycle step 1 (black circles represent carbon atoms) Calvin cycle steps 2 and 3 combined. The enzyme RuBisCO catalyses the carboxylation of ribulose-1,5-bisphosphate, RuBP, a 5-carbon compound, by carbon dioxide (a total of 6 carbons) in a two-step reaction. [6] The product of the first step is enediol-enzyme complex that can capture CO 2 ...
A reaction center comprises several (about 25-30) [6] protein subunits, which provide a scaffold for a series of cofactors. The cofactors can be pigments (like chlorophyll, pheophytin, carotenoids), quinones, or iron-sulfur clusters. [7] Each photosystem has two main subunits: an antenna complex (a light harvesting complex or LHC) and a ...
6 H 2 O + 6 CO 2 + energy → C 6 H 12 O 6 + 6 O 2 where C 6 H 12 O 6 is glucose (which is subsequently transformed into other sugars , starches , cellulose , lignin , and so forth). The value of the photosynthetic efficiency is dependent on how light energy is defined – it depends on whether we count only the light that is absorbed, and on ...
This center, below and to the left of the pair in the diagram, contains four manganese ions, a calcium ion, a chloride ion, and a tyrosine residue. Manganese is adept at these reactions because it is capable of existing in four oxidation states: Mn 2+, Mn 3+, Mn 4+ and Mn 5+. Manganese also forms strong bonds with oxygen-containing molecules ...
The oxygen-evolving complex is the site of water oxidation. It is a metallo-oxo cluster comprising four manganese ions (in oxidation states ranging from +3 to +4) [6] and one divalent calcium ion. When it oxidizes water, producing oxygen gas and protons, it sequentially delivers the four electrons from water to a tyrosine (D1-Y161) sidechain ...