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The principle that biological macromolecules catalyze a thermodynamically unfavorable reaction if and only if a thermodynamically favorable reaction occurs simultaneously, underlies all known forms of life. The transfer of electrons from a donor molecule to an acceptor molecule can be spatially separated into a series of intermediate redox ...
A hydrogen carrier is an organic macromolecule that transports atoms of hydrogen from one place to another inside a cell or from cell to cell for use in various metabolical processes. [1] Examples include NADPH , NADH , and FADH .
Plastoquinone (PQ) is a terpenoid-quinone (meroterpenoid) molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis.The most common form of plastoquinone, known as PQ-A or PQ-9, is a 2,3-dimethyl-1,4-benzoquinone molecule with a side chain of nine isoprenyl units.
Light-dependent reactions of photosynthesis at the thylakoid membrane. Light-dependent reactions are certain photochemical reactions involved in photosynthesis, the main process by which plants acquire energy. There are two light dependent reactions: the first occurs at photosystem II (PSII) and the second occurs at photosystem I (PSI).
At the reaction center, the electrons on the special chlorophyll molecule will be excited and ultimately transferred away by electron carriers. (If the electrons were not transferred away after excitation to a high energy state, they would lose energy by fluorescence back to the ground state, which would not allow plants to drive photosynthesis.)
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
By replenishing lost electrons with electrons from the splitting of water, photosystem II provides the electrons for all of photosynthesis to occur. The hydrogen ions (protons) generated by the oxidation of water help to create a proton gradient that is used by ATP synthase to generate ATP .
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.