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Carbon on Earth naturally occurs in two stable isotopes, with 98.9% in the form of 12 C and 1.1% in 13 C. [1] [8] The ratio between these isotopes varies in biological organisms due to metabolic processes that selectively use one carbon isotope over the other, or "fractionate" carbon through kinetic or thermodynamic effects. [1]
The evolution of oxygen during the light-dependent steps in photosynthesis (Hill reaction) was proposed and proven by British biochemist Robin Hill. He demonstrated that isolated chloroplasts would make oxygen (O 2) but not fix carbon dioxide (CO 2). This is evidence that the light and dark reactions occur at different sites within the cell. [1 ...
C 2 photosynthesis, an intermediate step between C 3 and Kranz C 4, may be preferred over C 4 for rice conversion. The simpler system is less optimized for high light and high temperature conditions than C 4, but has the advantage of requiring fewer steps of genetic engineering and performing better than C 3 under all temperatures and light ...
C 2 photosynthesis (also called glycine shuttle and photorespiratory CO 2 pump) is a CCM that works by making use of – as opposed to avoiding – photorespiration. It performs carbon refixation by delaying the breakdown of photorespired glycine, so that the molecule is shuttled from the mesophyll into the bundle sheath .
The underlying force driving these reactions is the Gibbs free energy of the reactants relative to the products. If donor and acceptor (the reactants) are of higher free energy than the reaction products, the electron transfer may occur spontaneously. The Gibbs free energy is the energy available ("free") to do work.
In oxygenic photosynthesis, the first electron donor is water, creating oxygen (O 2) as a by-product. In anoxygenic photosynthesis, various electron donors are used. Cytochrome b 6 f and ATP synthase work together to produce ATP (photophosphorylation) in two distinct ways.
The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as well as how it is used. The oxygen cycle is the biogeochemical cycle of oxygen atoms between different oxidation states in ions , oxides , and molecules through redox reactions within and between the spheres/reservoirs of the planet Earth. [ 1 ]
The thylakoid membrane is the site of the light-dependent reactions of photosynthesis with the photosynthetic pigments embedded directly in the membrane. It is an alternating pattern of dark and light bands measuring each 1 nanometre . [ 3 ]